Merge branch 'master' of https://github.com/z3prover/z3

CMakeLists.txt

@@ -34,7 +34,7 @@ endif()
 ################################################################################
 set(Z3_VERSION_MAJOR 4)
 set(Z3_VERSION_MINOR 8)
-set(Z3_VERSION_PATCH 1)
+set(Z3_VERSION_PATCH 2)
 set(Z3_VERSION_TWEAK 0)
 set(Z3_VERSION "${Z3_VERSION_MAJOR}.${Z3_VERSION_MINOR}.${Z3_VERSION_PATCH}.${Z3_VERSION_TWEAK}")
 set(Z3_FULL_VERSION_STR "${Z3_VERSION}") # Note this might be modified

cmake/msvc_legacy_quirks.cmake

@@ -8,13 +8,13 @@
 # FIXME: All the commented out defines should be removed once
 # we are confident it is correct to not set them.
 set(Z3_MSVC_LEGACY_DEFINES
-  # Don't set `_DEBUG`. The old build sytem sets this but this
+  # Don't set `_DEBUG`. The old build system sets this but this
   # is wrong. MSVC will set this depending on which runtime is being used.
   # See https://msdn.microsoft.com/en-us/library/b0084kay.aspx
   # _DEBUG
 
   # The old build system only set `UNICODE` and `_UNICODE` for x86_64 release.
-  # That seems completly wrong so set it for all configurations.
+  # That seems completely wrong so set it for all configurations.
   # According to https://blogs.msdn.microsoft.com/oldnewthing/20040212-00/?p=40643/
   # `UNICODE` affects Windows headers and `_UNICODE` affects C runtime header files.
   # There is some discussion of this define at https://msdn.microsoft.com/en-us/library/dybsewaf.aspx
@@ -116,7 +116,7 @@ z3_add_cxx_flag("/analyze-" REQUIRED)
 ################################################################################
 
 # By default CMake enables incremental linking for Debug and RelWithDebInfo
-# builds. The old build sytem disables it for all builds so try to do the same
+# builds. The old build system disables it for all builds so try to do the same
 # by changing all configurations if necessary
 string(TOUPPER "${available_build_types}" _build_types_as_upper)
 foreach (_build_type ${_build_types_as_upper})

cmake/z3_add_component.cmake

@@ -7,7 +7,7 @@ function(z3_expand_dependencies output_var)
   if (ARGC LESS 2)
     message(FATAL_ERROR "Invalid number of arguments")
   endif()
-  # Remaing args should be component names
+  # Remaining args should be component names
   set(_expanded_deps ${ARGN})
   set(_old_number_of_deps 0)
   list(LENGTH _expanded_deps _number_of_deps)
@@ -33,7 +33,7 @@ function(z3_add_component_dependencies_to_target target_name)
   if (NOT (TARGET ${target_name}))
     message(FATAL_ERROR "Target \"${target_name}\" does not exist")
   endif()
-  # Remaing args should be component names
+  # Remaining args should be component names
   set(_expanded_deps ${ARGN})
   foreach (dependency ${_expanded_deps})
     # Ensure this component's dependencies are built before this component.
@@ -219,7 +219,7 @@ macro(z3_add_component component_name)
   # Record this component's dependencies
   foreach (dependency ${Z3_MOD_COMPONENT_DEPENDENCIES})
     if (NOT (TARGET ${dependency}))
-      message(FATAL_ERROR "Component \"${component_name}\" depends on a non existant component \"${dependency}\"")
+      message(FATAL_ERROR "Component \"${component_name}\" depends on a non existent component \"${dependency}\"")
     endif()
     set_property(GLOBAL APPEND PROPERTY Z3_${component_name}_DEPS "${dependency}")
   endforeach()

contrib/ci/README.md

@@ -1,4 +1,4 @@
-# Continous integration scripts
+# Continuous integration scripts
 
 ## TravisCI
 
@@ -45,7 +45,7 @@ the future.
 * `Z3_VERBOSE_BUILD_OUTPUT` - Show compile commands in CMake builds (`0` or `1`)
 * `Z3_STATIC_BUILD` - Build Z3 binaries and libraries statically (`0` or `1`)
 * `Z3_SYSTEM_TEST_GIT_REVISION` - Git revision of [z3test](https://github.com/Z3Prover/z3test). If empty lastest revision will be used.
-* `Z3_WARNINGS_AS_ERRORS` - Set the `WARNINGS_AS_ERRORS` CMake option pased to Z3 (`OFF`, `ON`, or `SERIOUS_ONLY`)
+* `Z3_WARNINGS_AS_ERRORS` - Set the `WARNINGS_AS_ERRORS` CMake option passed to Z3 (`OFF`, `ON`, or `SERIOUS_ONLY`)
 
 ### Linux
 

doc/z3api.cfg.in

@@ -944,7 +944,7 @@ HTML_STYLESHEET        =
 # user-defined cascading style sheet that is included after the standard
 # style sheets created by doxygen. Using this option one can overrule
 # certain style aspects. This is preferred over using HTML_STYLESHEET
-# since it does not replace the standard style sheet and is therefor more
+# since it does not replace the standard style sheet and is therefore more
 # robust against future updates. Doxygen will copy the style sheet file to
 # the output directory.
 
@@ -1711,7 +1711,7 @@ UML_LOOK               = NO
 # the class node. If there are many fields or methods and many nodes the
 # graph may become too big to be useful. The UML_LIMIT_NUM_FIELDS
 # threshold limits the number of items for each type to make the size more
-# managable. Set this to 0 for no limit. Note that the threshold may be
+# manageable. Set this to 0 for no limit. Note that the threshold may be
 # exceeded by 50% before the limit is enforced.
 
 UML_LIMIT_NUM_FIELDS   = 10

examples/c++/CMakeLists.txt

@@ -7,8 +7,8 @@ find_package(Z3
   REQUIRED
   CONFIG
   # `NO_DEFAULT_PATH` is set so that -DZ3_DIR has to be passed to find Z3.
-  # This should prevent us from accidently picking up an installed
+  # This should prevent us from accidentally picking up an installed
-  # copy of Z3. This is here to benefit Z3's build sytem when building
+  # copy of Z3. This is here to benefit Z3's build system when building
   # this project. When making your own project you probably shouldn't
   # use this option.
   NO_DEFAULT_PATH

examples/c++/example.cpp

@@ -835,6 +835,17 @@ void tst_visit() {
     visit(f);
 }
 
+void tst_numeral() {
+    context c;
+    expr x = c.real_val("1/3");
+    double d = 0;
+    if (!x.is_numeral(d)) {
+        std::cout << x << " is not recognized as a numeral\n";
+        return;
+    }
+    std::cout << x << " is " << d << "\n";
+}
+
 void incremental_example1() {
     std::cout << "incremental example1\n";
     context c;
@@ -1212,6 +1223,7 @@ int main() {
         tactic_example9(); std::cout << "\n";
         tactic_qe(); std::cout << "\n";
         tst_visit(); std::cout << "\n";
+        tst_numeral(); std::cout << "\n";
         incremental_example1(); std::cout << "\n";
         incremental_example2(); std::cout << "\n";
         incremental_example3(); std::cout << "\n";

examples/c/CMakeLists.txt

@@ -24,8 +24,8 @@ find_package(Z3
   REQUIRED
   CONFIG
   # `NO_DEFAULT_PATH` is set so that -DZ3_DIR has to be passed to find Z3.
-  # This should prevent us from accidently picking up an installed
+  # This should prevent us from accidentally picking up an installed
-  # copy of Z3. This is here to benefit Z3's build sytem when building
+  # copy of Z3. This is here to benefit Z3's build system when building
   # this project. When making your own project you probably shouldn't
   # use this option.
   NO_DEFAULT_PATH

examples/dotnet/Program.cs

@@ -363,10 +363,10 @@ namespace test_mapi
 
             Console.WriteLine("Model = " + s.Model);
 
-            Console.WriteLine("Interpretation of MyArray:\n" + s.Model.FuncInterp(aex.FuncDecl));
+            //Console.WriteLine("Interpretation of MyArray:\n" + s.Model.ConstInterp(aex.FuncDecl));
             Console.WriteLine("Interpretation of x:\n" + s.Model.ConstInterp(xc));
             Console.WriteLine("Interpretation of f:\n" + s.Model.FuncInterp(fd));
-            Console.WriteLine("Interpretation of MyArray as Term:\n" + s.Model.FuncInterp(aex.FuncDecl));
+            //Console.WriteLine("Interpretation of MyArray as Term:\n" + s.Model.ConstInterp(aex.FuncDecl));
         }
 
         /// <summary>

examples/maxsat/CMakeLists.txt

@@ -11,8 +11,8 @@ find_package(Z3
   REQUIRED
   CONFIG
   # `NO_DEFAULT_PATH` is set so that -DZ3_DIR has to be passed to find Z3.
-  # This should prevent us from accidently picking up an installed
+  # This should prevent us from accidentally picking up an installed
-  # copy of Z3. This is here to benefit Z3's build sytem when building
+  # copy of Z3. This is here to benefit Z3's build system when building
   # this project. When making your own project you probably shouldn't
   # use this option.
   NO_DEFAULT_PATH

examples/msf/SolverFoundation.Plugin.Z3/Z3BaseSolver.cs

@@ -226,7 +226,7 @@ namespace Microsoft.SolverFoundation.Plugin.Z3
         }
 
         /// <summary>
-        /// Adds a MSF variable with the coresponding assertion to the Z3 variables.
+        /// Adds a MSF variable with the corresponding assertion to the Z3 variables.
         /// </summary>
         /// <param name="vid">The MSF id of the variable</param>
         internal void AddVariable(int vid)

examples/tptp/CMakeLists.txt

@@ -7,8 +7,8 @@ find_package(Z3
   REQUIRED
   CONFIG
   # `NO_DEFAULT_PATH` is set so that -DZ3_DIR has to be passed to find Z3.
-  # This should prevent us from accidently picking up an installed
+  # This should prevent us from accidentally picking up an installed
-  # copy of Z3. This is here to benefit Z3's build sytem when building
+  # copy of Z3. This is here to benefit Z3's build system when building
   # this project. When making your own project you probably shouldn't
   # use this option.
   NO_DEFAULT_PATH

examples/tptp/tptp5.cpp

@@ -233,7 +233,7 @@ class env {
 
     void check_arity(unsigned num_args, unsigned arity) {
         if (num_args != arity) {
-            throw failure_ex("arity missmatch");
+            throw failure_ex("arity mismatch");
         }
     }
 

scripts/mk_project.py

@@ -9,7 +9,7 @@ from mk_util import *
 
 # Z3 Project definition
 def init_project_def():
-    set_version(4, 8, 1, 0)
+    set_version(4, 8, 2, 0)
     add_lib('util', [], includes2install = ['z3_version.h'])
     add_lib('polynomial', ['util'], 'math/polynomial')
     add_lib('sat', ['util'])

scripts/mk_util.py

@@ -3494,7 +3494,7 @@ class MakeRuleCmd(object):
         needed commands used in Makefile rules
         Note that several of the method are meant for use during ``make
         install`` and ``make uninstall``.  These methods correctly use
-        ``$(PREFIX)`` and ``$(DESTDIR)`` and therefore are preferrable
+        ``$(PREFIX)`` and ``$(DESTDIR)`` and therefore are preferable
         to writing commands manually which can be error prone.
     """
     @classmethod

src/ackermannization/lackr_model_constructor.cpp

@@ -276,7 +276,7 @@ struct lackr_model_constructor::imp {
             SASSERT(a->get_num_args() == 0);
             func_decl * const fd = a->get_decl();
             expr * val = m_abstr_model->get_const_interp(fd);
-            if (val == nullptr) { // TODO: avoid model completetion?
+            if (val == nullptr) { // TODO: avoid model completion?
                 sort * s = fd->get_range();
                 val = m_abstr_model->get_some_value(s);
             }

src/api/api_context.cpp

@@ -219,7 +219,7 @@ namespace api {
         if (m_user_ref_count) {
             // Corner case bug: n may be in m_last_result, and this is the only reference to n.
             // When, we execute reset() it is deleted
-            // To avoid this bug, I bump the reference counter before reseting m_last_result
+            // To avoid this bug, I bump the reference counter before resetting m_last_result
             ast_ref node(n, m());
             m_last_result.reset();
             m_last_result.push_back(std::move(node));

src/api/api_datalog.cpp

@@ -210,7 +210,7 @@ extern "C" {
         if (!out) {
             return Z3_FALSE;
         }
-        // must start loggging here, since function uses Z3_get_sort_kind above
+        // must start logging here, since function uses Z3_get_sort_kind above
         LOG_Z3_get_finite_domain_sort_size(c, s, out);
         RESET_ERROR_CODE();  
         VERIFY(mk_c(c)->datalog_util().try_get_size(to_sort(s), *out));

src/api/api_numeral.cpp

@@ -227,6 +227,11 @@ extern "C" {
         Z3_CATCH_RETURN("");
     }
 
+    double Z3_API Z3_get_numeral_double(Z3_context c, Z3_ast a) {
+        Z3_string s = Z3_get_numeral_decimal_string(c, a, 12);
+        return std::stod(std::string(s));
+    }
+
     Z3_string Z3_API Z3_get_numeral_decimal_string(Z3_context c, Z3_ast a, unsigned precision) {
         Z3_TRY;
         LOG_Z3_get_numeral_decimal_string(c, a, precision);

src/api/c++/z3++.h

@@ -709,6 +709,7 @@ namespace z3 {
         bool is_numeral_u(unsigned& i) const { bool r = 0 != Z3_get_numeral_uint(ctx(), m_ast, &i); check_error(); return r;}
         bool is_numeral(std::string& s) const { if (!is_numeral()) return false; s = Z3_get_numeral_string(ctx(), m_ast); check_error(); return true; }
         bool is_numeral(std::string& s, unsigned precision) const { if (!is_numeral()) return false; s = Z3_get_numeral_decimal_string(ctx(), m_ast, precision); check_error(); return true; }
+        bool is_numeral(double& d) const { if (!is_numeral()) return false; d = Z3_get_numeral_double(ctx(), m_ast); check_error(); return true; }
         /**
            \brief Return true if this expression is an application.
         */

src/api/dotnet/AST.cs

@@ -17,17 +17,16 @@ Notes:
 
 --*/
 
+using System.Diagnostics;
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// The abstract syntax tree (AST) class.
     /// </summary>
-    [ContractVerification(true)]
     public class AST : Z3Object, IComparable
     {
         /// <summary>
@@ -114,8 +113,7 @@ namespace Microsoft.Z3
         /// <returns>A copy of the AST which is associated with <paramref name="ctx"/></returns>
         public AST Translate(Context ctx)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Ensures(Contract.Result<AST>() != null);
 
             if (ReferenceEquals(Context, ctx))
                 return this;
@@ -202,14 +200,13 @@ namespace Microsoft.Z3
         /// </summary>
         public string SExpr()
         {
-            Contract.Ensures(Contract.Result<string>() != null);
 
             return Native.Z3_ast_to_string(Context.nCtx, NativeObject);
         }
 
         #region Internal
-        internal AST(Context ctx) : base(ctx) { Contract.Requires(ctx != null); }
+        internal AST(Context ctx) : base(ctx) { Debug.Assert(ctx != null); }
-        internal AST(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal AST(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
         internal class DecRefQueue : IDecRefQueue
         {
@@ -246,8 +243,7 @@ namespace Microsoft.Z3
 
         internal static AST Create(Context ctx, IntPtr obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Ensures(Contract.Result<AST>() != null);
 
             switch ((Z3_ast_kind)Native.Z3_get_ast_kind(ctx.nCtx, obj))
             {

src/api/dotnet/ASTMap.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Map from AST to AST
     /// </summary>
-    [ContractVerification(true)]
     internal class ASTMap : Z3Object
     {
         /// <summary>
@@ -35,7 +34,7 @@ namespace Microsoft.Z3
         /// <returns>True if <paramref name="k"/> is a key in the map, false otherwise.</returns>
         public bool Contains(AST k)
         {
-            Contract.Requires(k != null);
+            Debug.Assert(k != null);
 
             return 0 != Native.Z3_ast_map_contains(Context.nCtx, NativeObject, k.NativeObject);
         }
@@ -49,8 +48,7 @@ namespace Microsoft.Z3
         /// <param name="k">An AST</param>    
         public AST Find(AST k)
         {
-            Contract.Requires(k != null);
+            Debug.Assert(k != null);
-            Contract.Ensures(Contract.Result<AST>() != null);
 
             return new AST(Context, Native.Z3_ast_map_find(Context.nCtx, NativeObject, k.NativeObject));
         }
@@ -62,8 +60,8 @@ namespace Microsoft.Z3
         /// <param name="v">The value AST</param>
         public void Insert(AST k, AST v)
         {
-            Contract.Requires(k != null);
+            Debug.Assert(k != null);
-            Contract.Requires(v != null);
+            Debug.Assert(v != null);
 
             Native.Z3_ast_map_insert(Context.nCtx, NativeObject, k.NativeObject, v.NativeObject);
         }
@@ -74,7 +72,7 @@ namespace Microsoft.Z3
         /// <param name="k">An AST</param>
         public void Erase(AST k)
         {
-            Contract.Requires(k != null);
+            Debug.Assert(k != null);
 
             Native.Z3_ast_map_erase(Context.nCtx, NativeObject, k.NativeObject);
         }
@@ -119,12 +117,12 @@ namespace Microsoft.Z3
         internal ASTMap(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal ASTMap(Context ctx)
             : base(ctx, Native.Z3_mk_ast_map(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/ASTVector.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -45,13 +45,12 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<AST>() != null);
 
                 return new AST(Context, Native.Z3_ast_vector_get(Context.nCtx, NativeObject, i));
             }
             set
             {
-                Contract.Requires(value != null);
+                Debug.Assert(value != null);
 
                 Native.Z3_ast_vector_set(Context.nCtx, NativeObject, i, value.NativeObject);
             }
@@ -73,7 +72,7 @@ namespace Microsoft.Z3
         /// <param name="a">An AST</param>
         public void Push(AST a)
         {
-            Contract.Requires(a != null);
+            Debug.Assert(a != null);
 
             Native.Z3_ast_vector_push(Context.nCtx, NativeObject, a.NativeObject);
         }
@@ -85,8 +84,7 @@ namespace Microsoft.Z3
         /// <returns>A new ASTVector</returns>
         public ASTVector Translate(Context ctx)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Ensures(Contract.Result<ASTVector>() != null);
 
             return new ASTVector(Context, Native.Z3_ast_vector_translate(Context.nCtx, NativeObject, ctx.nCtx));
         }
@@ -232,8 +230,8 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        internal ASTVector(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal ASTVector(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
-        internal ASTVector(Context ctx) : base(ctx, Native.Z3_mk_ast_vector(ctx.nCtx)) { Contract.Requires(ctx != null); }
+        internal ASTVector(Context ctx) : base(ctx, Native.Z3_mk_ast_vector(ctx.nCtx)) { Debug.Assert(ctx != null); }
 
         internal class DecRefQueue : IDecRefQueue
         {

src/api/dotnet/AlgebraicNum.cs

@@ -16,8 +16,8 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 #if !FRAMEWORK_LT_4
 using System.Numerics;
@@ -28,7 +28,6 @@ namespace Microsoft.Z3
     /// <summary>
     /// Algebraic numbers
     /// </summary>
-    [ContractVerification(true)]
     public class AlgebraicNum : ArithExpr
     {
         /// <summary>
@@ -40,7 +39,6 @@ namespace Microsoft.Z3
         /// <returns>A numeral Expr of sort Real</returns>
         public RatNum ToUpper(uint precision)
         {
-            Contract.Ensures(Contract.Result<RatNum>() != null);
 
             return new RatNum(Context, Native.Z3_get_algebraic_number_upper(Context.nCtx, NativeObject, precision));
         }
@@ -54,7 +52,6 @@ namespace Microsoft.Z3
         /// <returns>A numeral Expr of sort Real</returns>
         public RatNum ToLower(uint precision)
         {
-            Contract.Ensures(Contract.Result<RatNum>() != null);
 
             return new RatNum(Context, Native.Z3_get_algebraic_number_lower(Context.nCtx, NativeObject, precision));
         }
@@ -65,7 +62,6 @@ namespace Microsoft.Z3
         /// <remarks>The result has at most <paramref name="precision"/> decimal places.</remarks>    
         public string ToDecimal(uint precision)
         {
-            Contract.Ensures(Contract.Result<string>() != null);
 
             return Native.Z3_get_numeral_decimal_string(Context.nCtx, NativeObject, precision);
         }
@@ -74,7 +70,7 @@ namespace Microsoft.Z3
         internal AlgebraicNum(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/ApplyResult.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -26,7 +26,6 @@ namespace Microsoft.Z3
     /// ApplyResult objects represent the result of an application of a 
     /// tactic to a goal. It contains the subgoals that were produced.
     /// </summary>
-    [ContractVerification(true)]
     public class ApplyResult : Z3Object
     {
         /// <summary>
@@ -44,8 +43,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Goal[]>() != null);
-                Contract.Ensures(Contract.Result<Goal[]>().Length == this.NumSubgoals);
 
                 uint n = NumSubgoals;
                 Goal[] res = new Goal[n];
@@ -67,7 +64,7 @@ namespace Microsoft.Z3
         internal ApplyResult(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/ArithExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal ArithExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
 
@@ -45,7 +45,7 @@ namespace Microsoft.Z3
 
         private static ArithExpr MkNum(ArithExpr e, double d) { return (ArithExpr)e.Context.MkNumeral(d.ToString(), e.Context.MkRealSort()); }        
 
-        /// <summary> Operator overloading for arithmetical divsion operator (over reals) </summary>
+        /// <summary> Operator overloading for arithmetical division operator (over reals) </summary>
         public static ArithExpr operator /(ArithExpr a, ArithExpr b) { return a.Context.MkDiv(a, b); }
 
         /// <summary> Operator overloading for arithmetical operator </summary>

src/api/dotnet/ArithSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -28,7 +28,7 @@ namespace Microsoft.Z3
     public class ArithSort : Sort
     {
         #region Internal
-        internal ArithSort(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal ArithSort(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
         #endregion
     };
 }

src/api/dotnet/ArrayExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal ArrayExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion	
     }

src/api/dotnet/ArraySort.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Array sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class ArraySort : Sort
     {
         /// <summary>
@@ -35,7 +34,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort>() != null);
 
                 return Sort.Create(Context, Native.Z3_get_array_sort_domain(Context.nCtx, NativeObject));
             }
@@ -48,27 +46,26 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort>() != null);
 
                 return Sort.Create(Context, Native.Z3_get_array_sort_range(Context.nCtx, NativeObject));
             }
         }
 
         #region Internal
-        internal ArraySort(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal ArraySort(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
         internal ArraySort(Context ctx, Sort domain, Sort range)
             : base(ctx, Native.Z3_mk_array_sort(ctx.nCtx, domain.NativeObject, range.NativeObject))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(domain != null);
+            Debug.Assert(domain != null);
-            Contract.Requires(range != null);
+            Debug.Assert(range != null);
         }
         internal ArraySort(Context ctx, Sort[] domain, Sort range)
             : base(ctx, Native.Z3_mk_array_sort_n(ctx.nCtx, (uint)domain.Length, AST.ArrayToNative(domain), range.NativeObject))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(domain != null);
+            Debug.Assert(domain != null);
-            Contract.Requires(range != null);
+            Debug.Assert(range != null);
         }
         #endregion
     };

src/api/dotnet/BitVecExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -41,7 +41,7 @@ namespace Microsoft.Z3
 
         #region Internal
         /// <summary> Constructor for BitVecExpr </summary>
-        internal BitVecExpr(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal BitVecExpr(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
         #endregion
     }
 }

src/api/dotnet/BitVecNum.cs

@@ -16,8 +16,8 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 #if !FRAMEWORK_LT_4
 using System.Numerics;
@@ -28,7 +28,6 @@ namespace Microsoft.Z3
     /// <summary>
     /// Bit-vector numerals
     /// </summary>
-    [ContractVerification(true)]
     public class BitVecNum : BitVecExpr
     {
         /// <summary>
@@ -109,7 +108,7 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        internal BitVecNum(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal BitVecNum(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
         #endregion
     }
 }

src/api/dotnet/BitVecSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -36,7 +36,7 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        internal BitVecSort(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal BitVecSort(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
         #endregion
     };
 }

src/api/dotnet/BoolExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -32,7 +32,7 @@ namespace Microsoft.Z3
     {
         #region Internal
         /// <summary> Constructor for BoolExpr </summary>
-        internal BoolExpr(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal BoolExpr(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
         #endregion
 
         #region Operators

src/api/dotnet/BoolSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -28,8 +28,8 @@ namespace Microsoft.Z3
     public class BoolSort : Sort
     {
         #region Internal
-        internal BoolSort(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal BoolSort(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
-        internal BoolSort(Context ctx) : base(ctx, Native.Z3_mk_bool_sort(ctx.nCtx)) { Contract.Requires(ctx != null); }
+        internal BoolSort(Context ctx) : base(ctx, Native.Z3_mk_bool_sort(ctx.nCtx)) { Debug.Assert(ctx != null); }
         #endregion
     };
 }

src/api/dotnet/Constructor.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Constructors are used for datatype sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class Constructor : Z3Object
     {
         /// <summary>
@@ -46,7 +45,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 IntPtr constructor = IntPtr.Zero;
                 IntPtr tester = IntPtr.Zero;
                 IntPtr[] accessors = new IntPtr[n];
@@ -62,7 +60,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 IntPtr constructor = IntPtr.Zero;
                 IntPtr tester = IntPtr.Zero;
                 IntPtr[] accessors = new IntPtr[n];
@@ -78,7 +75,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
                 IntPtr constructor = IntPtr.Zero;
                 IntPtr tester = IntPtr.Zero;
                 IntPtr[] accessors = new IntPtr[n];
@@ -105,9 +101,9 @@ namespace Microsoft.Z3
                              Sort[] sorts, uint[] sortRefs)
             : base(ctx)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
-            Contract.Requires(recognizer != null);
+            Debug.Assert(recognizer != null);
 
             n = AST.ArrayLength(fieldNames);
 

src/api/dotnet/ConstructorList.cs

@@ -17,12 +17,12 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -43,14 +43,14 @@ namespace Microsoft.Z3
         internal ConstructorList(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal ConstructorList(Context ctx, Constructor[] constructors)
             : base(ctx)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(constructors != null);
+            Debug.Assert(constructors != null);
 
             NativeObject = Native.Z3_mk_constructor_list(Context.nCtx, (uint)constructors.Length, Constructor.ArrayToNative(constructors));
         }

src/api/dotnet/DatatypeExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal DatatypeExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/DatatypeSort.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Datatype sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class DatatypeSort : Sort
     {
         /// <summary>
@@ -43,7 +42,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
 
                 uint n = NumConstructors;
                 FuncDecl[] res = new FuncDecl[n];
@@ -60,7 +58,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
 
                 uint n = NumConstructors;
                 FuncDecl[] res = new FuncDecl[n];
@@ -77,7 +74,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[][]>() != null);
 
                 uint n = NumConstructors;
                 FuncDecl[][] res = new FuncDecl[n][];
@@ -95,14 +91,14 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        internal DatatypeSort(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal DatatypeSort(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
         internal DatatypeSort(Context ctx, Symbol name, Constructor[] constructors)
             : base(ctx, Native.Z3_mk_datatype(ctx.nCtx, name.NativeObject, (uint)constructors.Length, ArrayToNative(constructors)))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
-            Contract.Requires(constructors != null);
+            Debug.Assert(constructors != null);
         }
         #endregion
     };

src/api/dotnet/Deprecated.cs

@@ -17,17 +17,16 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// The main interaction with Z3 happens via the Context.
     /// </summary>
-    [ContractVerification(true)]
     public class Deprecated 
     {
 

src/api/dotnet/EnumSort.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Enumeration sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class EnumSort : Sort
     {
         /// <summary>
@@ -35,7 +34,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
                 uint n = Native.Z3_get_datatype_sort_num_constructors(Context.nCtx, NativeObject);
                 FuncDecl[] t = new FuncDecl[n];
                 for (uint i = 0; i < n; i++)
@@ -61,7 +59,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr[]>() != null);
                 FuncDecl[] cds = ConstDecls;
                 Expr[] t = new Expr[cds.Length];
                 for (uint i = 0; i < t.Length; i++)
@@ -87,7 +84,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
                 uint n = Native.Z3_get_datatype_sort_num_constructors(Context.nCtx, NativeObject);
                 FuncDecl[] t = new FuncDecl[n];
                 for (uint i = 0; i < n; i++)
@@ -110,9 +106,9 @@ namespace Microsoft.Z3
         internal EnumSort(Context ctx, Symbol name, Symbol[] enumNames)
             : base(ctx, IntPtr.Zero)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
-            Contract.Requires(enumNames != null);
+            Debug.Assert(enumNames != null);
 
             int n = enumNames.Length;
             IntPtr[] n_constdecls = new IntPtr[n];

src/api/dotnet/Expr.cs

@@ -17,15 +17,16 @@ Notes:
 
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
+using System.Linq;
+
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Expressions are terms.
     /// </summary>
-    [ContractVerification(true)]
     public class Expr : AST
     {
         /// <summary>
@@ -35,7 +36,6 @@ namespace Microsoft.Z3
         /// <seealso cref="Context.SimplifyHelp"/>
         public Expr Simplify(Params p = null)
         {
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             if (p == null)
                 return Expr.Create(Context, Native.Z3_simplify(Context.nCtx, NativeObject));
@@ -50,7 +50,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 return new FuncDecl(Context, Native.Z3_get_app_decl(Context.nCtx, NativeObject));
             }
         }
@@ -79,7 +78,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr[]>() != null);
 
                 uint n = NumArgs;
                 Expr[] res = new Expr[n];
@@ -94,7 +92,6 @@ namespace Microsoft.Z3
         /// </summary>
         public Expr Arg(uint i)
         {
-            Contract.Ensures(Contract.Result<Expr>() != null);
             return Expr.Create(Context, Native.Z3_get_app_arg(Context.nCtx, NativeObject, i));
         }
 
@@ -104,8 +101,8 @@ namespace Microsoft.Z3
         /// </summary>
         public void Update(Expr[] args)
         {
-            Contract.Requires(args != null);
+            Debug.Assert(args != null);
-            Contract.Requires(Contract.ForAll(args, a => a != null));
+            Debug.Assert(args.All(a => a != null));
 
             Context.CheckContextMatch<Expr>(args);
             if (IsApp && args.Length != NumArgs)
@@ -123,11 +120,10 @@ namespace Microsoft.Z3
         /// </remarks>
         public Expr Substitute(Expr[] from, Expr[] to)
         {
-            Contract.Requires(from != null);
+            Debug.Assert(from != null);
-            Contract.Requires(to != null);
+            Debug.Assert(to != null);
-            Contract.Requires(Contract.ForAll(from, f => f != null));
+            Debug.Assert(from.All(f => f != null));
-            Contract.Requires(Contract.ForAll(to, t => t != null));
+            Debug.Assert(to.All(t => t != null));
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             Context.CheckContextMatch<Expr>(from);
             Context.CheckContextMatch<Expr>(to);
@@ -142,9 +138,8 @@ namespace Microsoft.Z3
         /// <seealso cref="Substitute(Expr[],Expr[])"/>
         public Expr Substitute(Expr from, Expr to)
         {
-            Contract.Requires(from != null);
+            Debug.Assert(from != null);
-            Contract.Requires(to != null);
+            Debug.Assert(to != null);
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             return Substitute(new Expr[] { from }, new Expr[] { to });
         }
@@ -157,9 +152,8 @@ namespace Microsoft.Z3
         /// </remarks>
         public Expr SubstituteVars(Expr[] to)
         {
-            Contract.Requires(to != null);
+            Debug.Assert(to != null);
-            Contract.Requires(Contract.ForAll(to, t => t != null));
+            Debug.Assert(to.All(t => t != null));
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             Context.CheckContextMatch<Expr>(to);
             return Expr.Create(Context, Native.Z3_substitute_vars(Context.nCtx, NativeObject, (uint)to.Length, Expr.ArrayToNative(to)));
@@ -207,7 +201,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort>() != null);
                 return Sort.Create(Context, Native.Z3_get_sort(Context.nCtx, NativeObject));
             }
         }
@@ -332,7 +325,7 @@ namespace Microsoft.Z3
         /// <summary>
         /// Retrieve bound of at-most
         /// </summary>
-        public uint AtMostBound { get { Contract.Requires(IsAtMost); return (uint)FuncDecl.Parameters[0].Int; } }
+        public uint AtMostBound { get { Debug.Assert(IsAtMost); return (uint)FuncDecl.Parameters[0].Int; } }
 
         /// <summary>
         /// Indicates whether the term is at-least
@@ -342,7 +335,7 @@ namespace Microsoft.Z3
         /// <summary>
         /// Retrieve bound of at-least
         /// </summary>
-        public uint AtLeastBound { get { Contract.Requires(IsAtLeast); return (uint)FuncDecl.Parameters[0].Int; } }
+        public uint AtLeastBound { get { Debug.Assert(IsAtLeast); return (uint)FuncDecl.Parameters[0].Int; } }
 
         /// <summary>
         /// Indicates whether the term is pbeq
@@ -842,7 +835,7 @@ namespace Microsoft.Z3
         public string String { get { return Native.Z3_get_string(Context.nCtx, NativeObject); } }
 
         /// <summary>
-        /// Check whether expression is a concatentation.
+        /// Check whether expression is a concatenation.
         /// </summary>
         /// <returns>a Boolean</returns>
         public bool IsConcat { get { return IsApp && FuncDecl.DeclKind == Z3_decl_kind.Z3_OP_SEQ_CONCAT; } }
@@ -1816,8 +1809,6 @@ namespace Microsoft.Z3
                 if (!IsVar)
                     throw new Z3Exception("Term is not a bound variable.");
 
-                Contract.EndContractBlock();
-
                 return Native.Z3_get_index_value(Context.nCtx, NativeObject);
             }
         }
@@ -1827,10 +1818,9 @@ namespace Microsoft.Z3
         /// <summary>
         /// Constructor for Expr
         /// </summary>
-        internal protected Expr(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal protected Expr(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
 #if DEBUG
-        [Pure]
         internal override void CheckNativeObject(IntPtr obj)
         {
             if (Native.Z3_is_app(Context.nCtx, obj) == 0 &&
@@ -1841,12 +1831,10 @@ namespace Microsoft.Z3
         }
 #endif
 
-        [Pure]
         internal static Expr Create(Context ctx, FuncDecl f, params Expr[] arguments)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(f != null);
+            Debug.Assert(f != null);
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             IntPtr obj = Native.Z3_mk_app(ctx.nCtx, f.NativeObject,
                                           AST.ArrayLength(arguments),
@@ -1854,11 +1842,9 @@ namespace Microsoft.Z3
             return Create(ctx, obj);
         }
 
-        [Pure]
         new internal static Expr Create(Context ctx, IntPtr obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             Z3_ast_kind k = (Z3_ast_kind)Native.Z3_get_ast_kind(ctx.nCtx, obj);
             if (k == Z3_ast_kind.Z3_QUANTIFIER_AST)

src/api/dotnet/FPExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {    
@@ -45,7 +45,7 @@ namespace Microsoft.Z3
         internal FPExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/FPNum.cs

@@ -16,15 +16,14 @@ Author:
 Notes:
 
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// FloatiungPoint Numerals
     /// </summary>
-    [ContractVerification(true)]
     public class FPNum : FPExpr
     {
         /// <summary>
@@ -175,7 +174,7 @@ namespace Microsoft.Z3
         internal FPNum(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
 

src/api/dotnet/FPRMExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal FPRMExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/FPRMNum.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -93,7 +93,7 @@ namespace Microsoft.Z3
         internal FPRMNum(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/FPRMSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -31,12 +31,12 @@ namespace Microsoft.Z3
         internal FPRMSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal FPRMSort(Context ctx)
             : base(ctx, Native.Z3_mk_fpa_rounding_mode_sort(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/FPSort.cs

@@ -16,8 +16,8 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -40,12 +40,12 @@ namespace Microsoft.Z3
         internal FPSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal FPSort(Context ctx, uint ebits, uint sbits)
             : base(ctx, Native.Z3_mk_fpa_sort(ctx.nCtx, ebits, sbits))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }    

src/api/dotnet/FiniteDomainExpr.cs

@@ -16,8 +16,8 @@ Author:
 Notes:
 
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -31,7 +31,7 @@ namespace Microsoft.Z3
         internal FiniteDomainExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/FiniteDomainNum.cs

@@ -16,8 +16,8 @@ Author:
 Notes:
 
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 #if !FRAMEWORK_LT_4
 using System.Numerics;
@@ -28,7 +28,6 @@ namespace Microsoft.Z3
     /// <summary>
     /// Finite-domain numerals
     /// </summary>
-    [ContractVerification(true)]
     public class FiniteDomainNum : FiniteDomainExpr
     {
         /// <summary>
@@ -109,7 +108,7 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        internal FiniteDomainNum(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal FiniteDomainNum(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
         #endregion
     }
 }

src/api/dotnet/FiniteDomainSort.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Finite domain sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class FiniteDomainSort : Sort
     {
         /// <summary>
@@ -45,13 +44,13 @@ namespace Microsoft.Z3
         internal FiniteDomainSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal FiniteDomainSort(Context ctx, Symbol name, ulong size)
             : base(ctx, Native.Z3_mk_finite_domain_sort(ctx.nCtx, name.NativeObject, size))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
 
         }
         #endregion

src/api/dotnet/Fixedpoint.cs

@@ -18,14 +18,14 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
+using System.Linq;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Object for managing fixedpoints
     /// </summary>
-    [ContractVerification(true)]
     public class Fixedpoint : Z3Object
     {
 
@@ -36,7 +36,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<string>() != null);
                 return Native.Z3_fixedpoint_get_help(Context.nCtx, NativeObject);
             }
         }
@@ -48,7 +47,7 @@ namespace Microsoft.Z3
         {
             set
             {
-                Contract.Requires(value != null);
+                Debug.Assert(value != null);
                 Context.CheckContextMatch(value);
                 Native.Z3_fixedpoint_set_params(Context.nCtx, NativeObject, value.NativeObject);
             }
@@ -68,8 +67,8 @@ namespace Microsoft.Z3
         /// </summary>        
         public void Assert(params BoolExpr[] constraints)
         {
-            Contract.Requires(constraints != null);
+            Debug.Assert(constraints != null);
-            Contract.Requires(Contract.ForAll(constraints, c => c != null));
+            Debug.Assert(constraints.All(c => c != null));
 
             Context.CheckContextMatch<BoolExpr>(constraints);
             foreach (BoolExpr a in constraints)
@@ -91,7 +90,7 @@ namespace Microsoft.Z3
         /// </summary>       
         public void RegisterRelation(FuncDecl f)
         {
-            Contract.Requires(f != null);
+            Debug.Assert(f != null);
 
             Context.CheckContextMatch(f);
             Native.Z3_fixedpoint_register_relation(Context.nCtx, NativeObject, f.NativeObject);
@@ -102,7 +101,7 @@ namespace Microsoft.Z3
         /// </summary>        
         public void AddRule(BoolExpr rule, Symbol name = null)
         {
-            Contract.Requires(rule != null);
+            Debug.Assert(rule != null);
 
             Context.CheckContextMatch(rule);
             Native.Z3_fixedpoint_add_rule(Context.nCtx, NativeObject, rule.NativeObject, AST.GetNativeObject(name));
@@ -113,8 +112,8 @@ namespace Microsoft.Z3
         /// </summary>        
         public void AddFact(FuncDecl pred, params uint[] args)
         {
-            Contract.Requires(pred != null);
+            Debug.Assert(pred != null);
-            Contract.Requires(args != null);
+            Debug.Assert(args != null);
 
             Context.CheckContextMatch(pred);
             Native.Z3_fixedpoint_add_fact(Context.nCtx, NativeObject, pred.NativeObject, (uint)args.Length, args);
@@ -128,7 +127,7 @@ namespace Microsoft.Z3
         /// </summary>        
         public Status Query(BoolExpr query)
         {
-            Contract.Requires(query != null);
+            Debug.Assert(query != null);
 
             Context.CheckContextMatch(query);
             Z3_lbool r = (Z3_lbool)Native.Z3_fixedpoint_query(Context.nCtx, NativeObject, query.NativeObject);
@@ -148,8 +147,8 @@ namespace Microsoft.Z3
         /// </summary>        
         public Status Query(params FuncDecl[] relations)
         {
-            Contract.Requires(relations != null);
+            Debug.Assert(relations != null);
-            Contract.Requires(Contract.ForAll(0, relations.Length, i => relations[i] != null));
+            Debug.Assert(relations.All(rel => rel != null));
 
             Context.CheckContextMatch<FuncDecl>(relations);
             Z3_lbool r = (Z3_lbool)Native.Z3_fixedpoint_query_relations(Context.nCtx, NativeObject,
@@ -187,7 +186,7 @@ namespace Microsoft.Z3
         /// </summary>        
         public void UpdateRule(BoolExpr rule, Symbol name)
         {
-            Contract.Requires(rule != null);
+            Debug.Assert(rule != null);
 
             Context.CheckContextMatch(rule);
             Native.Z3_fixedpoint_update_rule(Context.nCtx, NativeObject, rule.NativeObject, AST.GetNativeObject(name));
@@ -208,7 +207,6 @@ namespace Microsoft.Z3
         /// </summary>                
         public string GetReasonUnknown()
         {
-            Contract.Ensures(Contract.Result<string>() != null);
 
             return Native.Z3_fixedpoint_get_reason_unknown(Context.nCtx, NativeObject);
         }
@@ -252,7 +250,7 @@ namespace Microsoft.Z3
         /// </summary>                
         public void SetPredicateRepresentation(FuncDecl f, Symbol[] kinds)
         {
-            Contract.Requires(f != null);
+            Debug.Assert(f != null);
 
             Native.Z3_fixedpoint_set_predicate_representation(Context.nCtx, NativeObject,
                                f.NativeObject, AST.ArrayLength(kinds), Symbol.ArrayToNative(kinds));
@@ -276,7 +274,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr[]>() != null);
 
                 ASTVector av = new ASTVector(Context, Native.Z3_fixedpoint_get_rules(Context.nCtx, NativeObject));
                 return av.ToBoolExprArray();
@@ -290,7 +287,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr[]>() != null);
 
                 ASTVector av = new ASTVector(Context, Native.Z3_fixedpoint_get_assertions(Context.nCtx, NativeObject));
                 return av.ToBoolExprArray();
@@ -304,7 +300,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Statistics>() != null);
 
                 return new Statistics(Context, Native.Z3_fixedpoint_get_statistics(Context.nCtx, NativeObject));
             }
@@ -335,12 +330,12 @@ namespace Microsoft.Z3
         internal Fixedpoint(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal Fixedpoint(Context ctx)
             : base(ctx, Native.Z3_mk_fixedpoint(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/FuncDecl.cs

@@ -18,14 +18,15 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
+using System.Linq;
+
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Function declarations.
     /// </summary>
-    [ContractVerification(true)]
     public class FuncDecl : AST
     {
         /// <summary>
@@ -108,7 +109,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort[]>() != null);
 
                 uint n = DomainSize;
 
@@ -126,7 +126,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort>() != null);
                 return Sort.Create(Context, Native.Z3_get_range(Context.nCtx, NativeObject));
             }
         }
@@ -146,7 +145,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Symbol>() != null);
                 return Symbol.Create(Context, Native.Z3_get_decl_name(Context.nCtx, NativeObject));
             }
         }
@@ -166,7 +164,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Parameter[]>() != null);
 
                 uint num = NumParameters;
                 Parameter[] res = new Parameter[num];
@@ -287,22 +284,22 @@ namespace Microsoft.Z3
         internal FuncDecl(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal FuncDecl(Context ctx, Symbol name, Sort[] domain, Sort range)
             : base(ctx, Native.Z3_mk_func_decl(ctx.nCtx, name.NativeObject, AST.ArrayLength(domain), AST.ArrayToNative(domain), range.NativeObject))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
-            Contract.Requires(range != null);
+            Debug.Assert(range != null);
         }
 
         internal FuncDecl(Context ctx, string prefix, Sort[] domain, Sort range)
             : base(ctx, Native.Z3_mk_fresh_func_decl(ctx.nCtx, prefix, AST.ArrayLength(domain), AST.ArrayToNative(domain), range.NativeObject))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(range != null);
+            Debug.Assert(range != null);
         }
 
 #if DEBUG
@@ -335,7 +332,7 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Requires(args == null || Contract.ForAll(args, a => a != null));
+                Debug.Assert(args == null || args.All(a => a != null));
 
                 return Apply(args);
             }
@@ -348,7 +345,7 @@ namespace Microsoft.Z3
         /// <returns></returns>
         public Expr Apply(params Expr[] args)
         {
-            Contract.Requires(args == null || Contract.ForAll(args, a => a != null));
+            Debug.Assert(args == null || args.All(a => a != null));
 
             Context.CheckContextMatch<Expr>(args);
             return Expr.Create(Context, this, args);

src/api/dotnet/FuncInterp.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -26,7 +26,6 @@ namespace Microsoft.Z3
     ///  A function interpretation is represented as a finite map and an 'else' value.
     ///  Each entry in the finite map represents the value of a function given a set of arguments.  
     /// </summary>
-    [ContractVerification(true)]
     public class FuncInterp : Z3Object
     {
         /// <summary>
@@ -42,7 +41,6 @@ namespace Microsoft.Z3
             {
                 get
                 {
-                    Contract.Ensures(Contract.Result<Expr>() != null);
                     return Expr.Create(Context, Native.Z3_func_entry_get_value(Context.nCtx, NativeObject));
                 }
             }
@@ -62,8 +60,6 @@ namespace Microsoft.Z3
             {
                 get
                 {
-                    Contract.Ensures(Contract.Result<Expr[]>() != null);
-                    Contract.Ensures(Contract.Result<Expr[]>().Length == this.NumArgs);
 
                     uint n = NumArgs;
                     Expr[] res = new Expr[n];
@@ -87,7 +83,7 @@ namespace Microsoft.Z3
             }
 
             #region Internal
-            internal Entry(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+            internal Entry(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
             internal class DecRefQueue : IDecRefQueue
             {
@@ -133,8 +129,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Entry[]>() != null);
-                Contract.Ensures(Contract.ForAll(0, Contract.Result<Entry[]>().Length, j => Contract.Result<Entry[]>()[j] != null));
 
                 uint n = NumEntries;
                 Entry[] res = new Entry[n];
@@ -151,7 +145,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr>() != null);
 
                 return Expr.Create(Context, Native.Z3_func_interp_get_else(Context.nCtx, NativeObject));
             }
@@ -194,7 +187,7 @@ namespace Microsoft.Z3
         internal FuncInterp(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/Global.cs

@@ -17,9 +17,9 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
 using System.Runtime.InteropServices;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {

src/api/dotnet/Goal.cs

@@ -18,7 +18,8 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
+using System.Linq;
 
 namespace Microsoft.Z3
 {
@@ -27,7 +28,6 @@ namespace Microsoft.Z3
     /// of formulas, that can be solved and/or transformed using
     /// tactics and solvers.
     /// </summary>
-    [ContractVerification(true)]
     public class Goal : Z3Object
     {
         /// <summary>
@@ -79,13 +79,13 @@ namespace Microsoft.Z3
         /// </summary>   
         public void Assert(params BoolExpr[] constraints)
         {
-            Contract.Requires(constraints != null);
+            Debug.Assert(constraints != null);
-            Contract.Requires(Contract.ForAll(constraints, c => c != null));
+            Debug.Assert(constraints.All(c => c != null));
 
             Context.CheckContextMatch<BoolExpr>(constraints);
             foreach (BoolExpr c in constraints)
             {
-                Contract.Assert(c != null); // It was an assume, now made an assert just to be sure we do not regress
+                Debug.Assert(c != null); // It was an assume, now made an assert just to be sure we do not regress
                 Native.Z3_goal_assert(Context.nCtx, NativeObject, c.NativeObject);
             }
         }
@@ -140,7 +140,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr[]>() != null);
 
                 uint n = Size;
                 BoolExpr[] res = new BoolExpr[n];
@@ -181,7 +180,6 @@ namespace Microsoft.Z3
         /// <returns>A model for <c>g</c></returns>
         public Model ConvertModel(Model m)
         {
-            Contract.Ensures(Contract.Result<Model>() != null);
             if (m != null)
                return new Model(Context, Native.Z3_goal_convert_model(Context.nCtx, NativeObject, m.NativeObject));
             else
@@ -194,7 +192,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Goal Translate(Context ctx)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
 
             return new Goal(ctx, Native.Z3_goal_translate(Context.nCtx, NativeObject, ctx.nCtx));
         }
@@ -248,12 +246,12 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        internal Goal(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal Goal(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
         internal Goal(Context ctx, bool models, bool unsatCores, bool proofs)
             : base(ctx, Native.Z3_mk_goal(ctx.nCtx, (byte)(models ? 1 : 0), (byte)(unsatCores ? 1 : 0), (byte)(proofs ? 1 : 0)))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/IDecRefQueue.cs

@@ -17,26 +17,24 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Threading;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// DecRefQueue interface
     /// </summary>
-    [ContractClass(typeof(DecRefQueueContracts))]
     public abstract class IDecRefQueue
     {
         #region Object invariant
 
-        [ContractInvariantMethod]
         private void ObjectInvariant()
         {
-            Contract.Invariant(this.m_queue != null);
+            Debug.Assert(this.m_queue != null);
         }
 
         #endregion
@@ -61,7 +59,7 @@ namespace Microsoft.Z3
 
         internal void IncAndClear(Context ctx, IntPtr o)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
 
             IncRef(ctx, o);
             if (m_queue.Count >= m_move_limit) Clear(ctx);
@@ -79,7 +77,7 @@ namespace Microsoft.Z3
 
         internal void Clear(Context ctx)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
 
             lock (m_lock)
             {
@@ -90,17 +88,16 @@ namespace Microsoft.Z3
         }
     }
 
-    [ContractClassFor(typeof(IDecRefQueue))]
     abstract class DecRefQueueContracts : IDecRefQueue
     {
         internal override void IncRef(Context ctx, IntPtr obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal override void DecRef(Context ctx, IntPtr obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
     }
 }

src/api/dotnet/IntExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal IntExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/IntNum.cs

@@ -16,8 +16,8 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 #if !FRAMEWORK_LT_4
 using System.Numerics;
@@ -28,7 +28,6 @@ namespace Microsoft.Z3
     /// <summary>
     /// Integer Numerals
     /// </summary>
-    [ContractVerification(true)]
     public class IntNum : IntExpr
     {
 
@@ -36,7 +35,7 @@ namespace Microsoft.Z3
         internal IntNum(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
 

src/api/dotnet/IntSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -31,12 +31,12 @@ namespace Microsoft.Z3
         internal IntSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal IntSort(Context ctx)
             : base(ctx, Native.Z3_mk_int_sort(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/IntSymbol.cs

@@ -18,15 +18,14 @@ Notes:
 --*/
 
 using System;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Numbered symbols
     /// </summary>
-    [ContractVerification(true)]
     public class IntSymbol : Symbol
     {
         /// <summary>
@@ -47,12 +46,12 @@ namespace Microsoft.Z3
         internal IntSymbol(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal IntSymbol(Context ctx, int i)
             : base(ctx, Native.Z3_mk_int_symbol(ctx.nCtx, i))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
 #if DEBUG

src/api/dotnet/Lambda.cs

@@ -18,14 +18,14 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
+using System.Linq;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Lambda expressions.
     /// </summary>
-    [ContractVerification(true)]
     public class Lambda : ArrayExpr
     {
         /// <summary>
@@ -43,7 +43,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Symbol[]>() != null);
 
                 uint n = NumBound;
                 Symbol[] res = new Symbol[n];
@@ -60,7 +59,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort[]>() != null);
 
                 uint n = NumBound;
                 Sort[] res = new Sort[n];
@@ -77,7 +75,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr>() != null);
 
                 return new BoolExpr(Context, Native.Z3_get_quantifier_body(Context.nCtx, NativeObject));
             }
@@ -94,17 +91,16 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        [ContractVerification(false)] // F: Clousot ForAll decompilation gets confused below. Setting verification off until I fixed the bug
         internal Lambda(Context ctx, Sort[] sorts, Symbol[] names, Expr body)
             : base(ctx, IntPtr.Zero)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(sorts != null);
+            Debug.Assert(sorts != null);
-            Contract.Requires(names != null);
+            Debug.Assert(names != null);
-            Contract.Requires(body != null);
+            Debug.Assert(body != null);
-            Contract.Requires(sorts.Length == names.Length);
+            Debug.Assert(sorts.Length == names.Length);
-            Contract.Requires(Contract.ForAll(sorts, s => s != null));
+            Debug.Assert(sorts.All(s => s != null));
-            Contract.Requires(Contract.ForAll(names, n => n != null));
+            Debug.Assert(names.All(n => n != null));
             Context.CheckContextMatch<Sort>(sorts);
             Context.CheckContextMatch<Symbol>(names);
             Context.CheckContextMatch(body);
@@ -119,14 +115,13 @@ namespace Microsoft.Z3
             
         }
 
-        [ContractVerification(false)] // F: Clousot ForAll decompilation gets confused below. Setting verification off until I fixed the bug
         internal Lambda(Context ctx, Expr[] bound, Expr body)
             : base(ctx, IntPtr.Zero)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(body != null);
+            Debug.Assert(body != null);
 
-            Contract.Requires(bound != null && bound.Length > 0 && Contract.ForAll(bound, n => n != null));
+            Debug.Assert(bound != null && bound.Length > 0 && bound.All(n => n != null));
 
             Context.CheckContextMatch<Expr>(bound);
             Context.CheckContextMatch(body);
@@ -137,7 +132,7 @@ namespace Microsoft.Z3
         }
 
 
-        internal Lambda(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal Lambda(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
 #if DEBUG
         internal override void CheckNativeObject(IntPtr obj)

src/api/dotnet/ListSort.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// List sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class ListSort : Sort
     {
         /// <summary>
@@ -35,7 +34,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 return new FuncDecl(Context, Native.Z3_get_datatype_sort_constructor(Context.nCtx, NativeObject, 0));                                
             }
         }
@@ -47,7 +45,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr>() != null);
                 return Context.MkApp(NilDecl);
             }
         }
@@ -59,7 +56,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 return new FuncDecl(Context, Native.Z3_get_datatype_sort_recognizer(Context.nCtx, NativeObject, 0));
             }
         }
@@ -71,7 +67,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 return new FuncDecl(Context, Native.Z3_get_datatype_sort_constructor(Context.nCtx, NativeObject, 1));
             }
         }
@@ -84,7 +79,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 return new FuncDecl(Context, Native.Z3_get_datatype_sort_recognizer(Context.nCtx, NativeObject, 1));
             }
         }
@@ -96,7 +90,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 return new FuncDecl(Context, Native.Z3_get_datatype_sort_constructor_accessor(Context.nCtx, NativeObject, 1, 0));
             }
         }
@@ -108,7 +101,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
                 return new FuncDecl(Context, Native.Z3_get_datatype_sort_constructor_accessor(Context.nCtx, NativeObject, 1, 1));
             }
         }
@@ -117,9 +109,9 @@ namespace Microsoft.Z3
         internal ListSort(Context ctx, Symbol name, Sort elemSort)
             : base(ctx, IntPtr.Zero)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
-            Contract.Requires(elemSort != null);
+            Debug.Assert(elemSort != null);
 
             IntPtr inil = IntPtr.Zero, iisnil = IntPtr.Zero, 
                    icons = IntPtr.Zero, iiscons = IntPtr.Zero,

src/api/dotnet/Log.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -29,7 +29,6 @@ namespace Microsoft.Z3
     /// Note that this is a global, static log and if multiple Context 
     /// objects are created, it logs the interaction with all of them.
     /// </remarks>
-    [ContractVerification(true)]
     public static class Log
     {
         private static bool m_is_open = false;
@@ -59,7 +58,7 @@ namespace Microsoft.Z3
         /// </summary>    
         public static void Append(string s)
         {
-            Contract.Requires(isOpen());
+            Debug.Assert(isOpen());
 
             if (!m_is_open)
                 throw new Z3Exception("Log cannot be closed.");
@@ -70,7 +69,6 @@ namespace Microsoft.Z3
         /// Checks whether the interaction log is opened.
         /// </summary>
         /// <returns>True if the interaction log is open, false otherwise.</returns>
-        [Pure]
         public static bool isOpen()
         {
             return m_is_open;

src/api/dotnet/Microsoft.Z3.csproj

@@ -342,6 +342,7 @@
     <Compile Include="ConstructorList.cs" />
     <Compile Include="DatatypeExpr.cs" />
     <Compile Include="DatatypeSort.cs" />
+    <Compile Include="Deprecated.cs" />
     <Compile Include="FiniteDomainExpr.cs" />
     <Compile Include="FiniteDomainNum.cs" />
     <Compile Include="FPExpr.cs" />
@@ -364,6 +365,7 @@
     <Compile Include="IntNum.cs" />
     <Compile Include="IntSort.cs" />
     <Compile Include="IntSymbol.cs" />
+    <Compile Include="Lambda.cs" />
     <Compile Include="ListSort.cs" />
     <Compile Include="Model.cs" />
     <Compile Include="Optimize.cs" />

src/api/dotnet/Model.cs

@@ -18,7 +18,7 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
 using System.Collections.Generic;
 
 namespace Microsoft.Z3
@@ -26,7 +26,6 @@ namespace Microsoft.Z3
     /// <summary>
     /// A Model contains interpretations (assignments) of constants and functions. 
     /// </summary>
-    [ContractVerification(true)]
     public class Model : Z3Object
     {
         /// <summary>
@@ -36,7 +35,7 @@ namespace Microsoft.Z3
         /// <returns>An expression if the constant has an interpretation in the model, null otherwise.</returns>
         public Expr ConstInterp(Expr a)
         {
-            Contract.Requires(a != null);
+            Debug.Assert(a != null);
 
             Context.CheckContextMatch(a);
             return ConstInterp(a.FuncDecl);
@@ -49,7 +48,7 @@ namespace Microsoft.Z3
         /// <returns>An expression if the function has an interpretation in the model, null otherwise.</returns>    
         public Expr ConstInterp(FuncDecl f)
         {
-            Contract.Requires(f != null);
+            Debug.Assert(f != null);
 
             Context.CheckContextMatch(f);
             if (f.Arity != 0 ||
@@ -70,7 +69,7 @@ namespace Microsoft.Z3
         /// <returns>A FunctionInterpretation if the function has an interpretation in the model, null otherwise.</returns> 
         public FuncInterp FuncInterp(FuncDecl f)
         {
-            Contract.Requires(f != null);
+            Debug.Assert(f != null);
 
             Context.CheckContextMatch(f);
 
@@ -122,7 +121,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
 
                 uint n = NumConsts;
                 FuncDecl[] res = new FuncDecl[n];
@@ -165,7 +163,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
 
                 uint n = NumFuncs;
                 FuncDecl[] res = new FuncDecl[n];
@@ -182,7 +179,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
 
                 uint nFuncs = NumFuncs;
                 uint nConsts = NumConsts;
@@ -223,8 +219,7 @@ namespace Microsoft.Z3
         /// <returns>The evaluation of <paramref name="t"/> in the model.</returns>        
         public Expr Eval(Expr t, bool completion = false)
         {
-            Contract.Requires(t != null);
+            Debug.Assert(t != null);
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             IntPtr v = IntPtr.Zero;
             if (Native.Z3_model_eval(Context.nCtx, NativeObject, t.NativeObject, (byte)(completion ? 1 : 0), ref v) == (byte)0)
@@ -238,8 +233,7 @@ namespace Microsoft.Z3
         /// </summary>        
         public Expr Evaluate(Expr t, bool completion = false)
         {
-            Contract.Requires(t != null);
+            Debug.Assert(t != null);
-            Contract.Ensures(Contract.Result<Expr>() != null);
 
             return Eval(t, completion);
         }
@@ -263,7 +257,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort[]>() != null);
 
                 uint n = NumSorts;
                 Sort[] res = new Sort[n];
@@ -281,8 +274,7 @@ namespace Microsoft.Z3
         /// <returns>An array of expressions, where each is an element of the universe of <paramref name="s"/></returns>
         public Expr[] SortUniverse(Sort s)
         {
-            Contract.Requires(s != null);
+            Debug.Assert(s != null);
-            Contract.Ensures(Contract.Result<Expr[]>() != null);
 
             ASTVector av = new ASTVector(Context, Native.Z3_model_get_sort_universe(Context.nCtx, NativeObject, s.NativeObject));            
             return av.ToExprArray();
@@ -301,7 +293,7 @@ namespace Microsoft.Z3
         internal Model(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/Optimize.cs

@@ -19,14 +19,14 @@ Notes:
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
+using System.Linq;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Object for managing optimizization context
     /// </summary>
-    [ContractVerification(true)]
     public class Optimize : Z3Object
     {
         /// <summary>
@@ -36,7 +36,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<string>() != null);
                 return Native.Z3_optimize_get_help(Context.nCtx, NativeObject);
             }
         }
@@ -48,7 +47,7 @@ namespace Microsoft.Z3
         {
             set
             {
-                Contract.Requires(value != null);
+                Debug.Assert(value != null);
                 Context.CheckContextMatch(value);
                 Native.Z3_optimize_set_params(Context.nCtx, NativeObject, value.NativeObject);
             }
@@ -99,8 +98,8 @@ namespace Microsoft.Z3
         /// </summary>   
         private void AddConstraints(IEnumerable<BoolExpr> constraints)
         {
-            Contract.Requires(constraints != null);
+            Debug.Assert(constraints != null);
-            Contract.Requires(Contract.ForAll(constraints, c => c != null));
+            Debug.Assert(constraints.All(c => c != null));
 
             Context.CheckContextMatch(constraints);
             foreach (BoolExpr a in constraints)
@@ -248,7 +247,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr[]>() != null);
 
                 ASTVector core = new ASTVector(Context, Native.Z3_optimize_get_unsat_core(Context.nCtx, NativeObject));                
                 return core.ToBoolExprArray();
@@ -319,7 +317,6 @@ namespace Microsoft.Z3
         {
             get 
             {
-                Contract.Ensures(Contract.Result<string>() != null);
                 return Native.Z3_optimize_get_reason_unknown(Context.nCtx, NativeObject);
             }
         }
@@ -357,7 +354,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr[]>() != null);
 
                 ASTVector assertions = new ASTVector(Context, Native.Z3_optimize_get_assertions(Context.nCtx, NativeObject));
                 return assertions.ToBoolExprArray();
@@ -371,7 +367,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr[]>() != null);
 
                 ASTVector objectives = new ASTVector(Context, Native.Z3_optimize_get_objectives(Context.nCtx, NativeObject));
                 return objectives.ToExprArray();
@@ -386,7 +381,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Statistics>() != null);
 
                 return new Statistics(Context, Native.Z3_optimize_get_statistics(Context.nCtx, NativeObject));
             }
@@ -397,12 +391,12 @@ namespace Microsoft.Z3
         internal Optimize(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal Optimize(Context ctx)
             : base(ctx, Native.Z3_mk_optimize(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/ParamDescrs.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// A ParamDescrs describes a set of parameters.
     /// </summary>
-    [ContractVerification(true)]
     public class ParamDescrs : Z3Object
     {
         /// <summary>
@@ -33,7 +32,7 @@ namespace Microsoft.Z3
         /// </summary>
         public void Validate(Params p)
         {
-            Contract.Requires(p != null);
+            Debug.Assert(p != null);
             Native.Z3_params_validate(Context.nCtx, p.NativeObject, NativeObject);
         }
 
@@ -42,7 +41,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Z3_param_kind GetKind(Symbol name)
         {
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
             return (Z3_param_kind)Native.Z3_param_descrs_get_kind(Context.nCtx, NativeObject, name.NativeObject);
         }
 
@@ -51,7 +50,7 @@ namespace Microsoft.Z3
         /// </summary>
         public string GetDocumentation(Symbol name)
         {
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
             return Native.Z3_param_descrs_get_documentation(Context.nCtx, NativeObject, name.NativeObject);
         }
 
@@ -91,7 +90,7 @@ namespace Microsoft.Z3
         internal ParamDescrs(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/Params.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// A Params objects represents a configuration in the form of Symbol/value pairs.
     /// </summary>
-    [ContractVerification(true)]
     public class Params : Z3Object
     {
         /// <summary>
@@ -33,7 +32,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Params Add(Symbol name, bool value)
         {
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
 
             Native.Z3_params_set_bool(Context.nCtx, NativeObject, name.NativeObject, (byte)(value ? 1 : 0));
             return this;
@@ -44,7 +43,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Params Add(Symbol name, uint value)
         {
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
 
             Native.Z3_params_set_uint(Context.nCtx, NativeObject, name.NativeObject, value);
             return this;
@@ -55,7 +54,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Params Add(Symbol name, double value)
         {
-            Contract.Requires(name != null);            
+            Debug.Assert(name != null);            
 
             Native.Z3_params_set_double(Context.nCtx, NativeObject, name.NativeObject, value);
             return this;
@@ -66,7 +65,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Params Add(Symbol name, string value)
         {
-            Contract.Requires(value != null);
+            Debug.Assert(value != null);
 
             Native.Z3_params_set_symbol(Context.nCtx, NativeObject, name.NativeObject, Context.MkSymbol(value).NativeObject);
             return this;
@@ -77,8 +76,8 @@ namespace Microsoft.Z3
         /// </summary>
         public Params Add(Symbol name, Symbol value)
         {
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
-            Contract.Requires(value != null);
+            Debug.Assert(value != null);
 
             Native.Z3_params_set_symbol(Context.nCtx, NativeObject, name.NativeObject, value.NativeObject);
             return this;
@@ -117,7 +116,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Params Add(string name, Symbol value)
         {
-            Contract.Requires(value != null);
+            Debug.Assert(value != null);
 
             Native.Z3_params_set_symbol(Context.nCtx, NativeObject, Context.MkSymbol(name).NativeObject, value.NativeObject);
             return this;
@@ -128,8 +127,8 @@ namespace Microsoft.Z3
         /// </summary>
         public Params Add(string name, string value)
         {
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
-            Contract.Requires(value != null);
+            Debug.Assert(value != null);
 
             Native.Z3_params_set_symbol(Context.nCtx, NativeObject, Context.MkSymbol(name).NativeObject, Context.MkSymbol(value).NativeObject);
             return this;
@@ -147,7 +146,7 @@ namespace Microsoft.Z3
         internal Params(Context ctx)
             : base(ctx, Native.Z3_mk_params(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/Pattern.cs

@@ -17,9 +17,9 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
 using System.Runtime.InteropServices;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -28,7 +28,6 @@ namespace Microsoft.Z3
     /// non-empty.  If the list comprises of more than one term, it is
     /// also called a multi-pattern.
     /// </summary>
-    [ContractVerification(true)]
     public class Pattern : AST
     {
         /// <summary>
@@ -46,7 +45,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr[]>() != null);
 
                 uint n = NumTerms;
                 Expr[] res = new Expr[n];
@@ -68,7 +66,7 @@ namespace Microsoft.Z3
         internal Pattern(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/Probe.cs

@@ -17,9 +17,9 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
 using System.Runtime.InteropServices;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -30,7 +30,6 @@ namespace Microsoft.Z3
     /// and <c>Context.ProbeNames</c>.
     /// It may also be obtained using the command <c>(help-tactic)</c> in the SMT 2.0 front-end.
     /// </summary>
-    [ContractVerification(true)]
     public class Probe : Z3Object
     {
         /// <summary>
@@ -40,7 +39,7 @@ namespace Microsoft.Z3
         /// "Boolean" probes return 0.0 for false, and a value different from 0.0 for true.</returns>
         public double Apply(Goal g)
         {
-            Contract.Requires(g != null);
+            Debug.Assert(g != null);
 
             Context.CheckContextMatch(g);
             return Native.Z3_probe_apply(Context.nCtx, NativeObject, g.NativeObject);
@@ -53,7 +52,7 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Requires(g != null);
+                Debug.Assert(g != null);
 
                 return Apply(g);
             }
@@ -63,12 +62,12 @@ namespace Microsoft.Z3
         internal Probe(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal Probe(Context ctx, string name)
             : base(ctx, Native.Z3_mk_probe(ctx.nCtx, name))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/Quantifier.cs

@@ -18,14 +18,14 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
+using System.Linq;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Quantifier expressions.
     /// </summary>
-    [ContractVerification(true)]
     public class Quantifier : BoolExpr
     {
         /// <summary>
@@ -67,7 +67,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Pattern[]>() != null);
 
                 uint n = NumPatterns;
                 Pattern[] res = new Pattern[n];
@@ -92,7 +91,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Pattern[]>() != null);
 
                 uint n = NumNoPatterns;
                 Pattern[] res = new Pattern[n];
@@ -117,7 +115,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Symbol[]>() != null);
 
                 uint n = NumBound;
                 Symbol[] res = new Symbol[n];
@@ -134,7 +131,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort[]>() != null);
 
                 uint n = NumBound;
                 Sort[] res = new Sort[n];
@@ -151,7 +147,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr>() != null);
 
                 return new BoolExpr(Context, Native.Z3_get_quantifier_body(Context.nCtx, NativeObject));
             }
@@ -168,19 +163,18 @@ namespace Microsoft.Z3
         }
 
         #region Internal
-        [ContractVerification(false)] // F: Clousot ForAll decompilation gets confused below. Setting verification off until I fixed the bug
         internal Quantifier(Context ctx, bool isForall, Sort[] sorts, Symbol[] names, Expr body, uint weight = 1, Pattern[] patterns = null, Expr[] noPatterns = null, Symbol quantifierID = null, Symbol skolemID = null)
             : base(ctx, IntPtr.Zero)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(sorts != null);
+            Debug.Assert(sorts != null);
-            Contract.Requires(names != null);
+            Debug.Assert(names != null);
-            Contract.Requires(body != null);
+            Debug.Assert(body != null);
-            Contract.Requires(sorts.Length == names.Length);
+            Debug.Assert(sorts.Length == names.Length);
-            Contract.Requires(Contract.ForAll(sorts, s => s != null));
+            Debug.Assert(sorts.All(s => s != null));
-            Contract.Requires(Contract.ForAll(names, n => n != null));
+            Debug.Assert(names.All(n => n != null));
-            Contract.Requires(patterns == null || Contract.ForAll(patterns, p => p != null));
+            Debug.Assert(patterns == null || patterns.All(p => p != null));
-            Contract.Requires(noPatterns == null || Contract.ForAll(noPatterns, np => np != null));
+            Debug.Assert(noPatterns == null || noPatterns.All(np => np != null));
 
             Context.CheckContextMatch<Pattern>(patterns);
             Context.CheckContextMatch<Expr>(noPatterns);
@@ -211,16 +205,15 @@ namespace Microsoft.Z3
             }
         }
 
-        [ContractVerification(false)] // F: Clousot ForAll decompilation gets confused below. Setting verification off until I fixed the bug
         internal Quantifier(Context ctx, bool isForall, Expr[] bound, Expr body, uint weight = 1, Pattern[] patterns = null, Expr[] noPatterns = null, Symbol quantifierID = null, Symbol skolemID = null)
             : base(ctx, IntPtr.Zero)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(body != null);
+            Debug.Assert(body != null);
 
-            Contract.Requires(patterns == null || Contract.ForAll(patterns, p => p != null));
+            Debug.Assert(patterns == null || patterns.All(p => p != null));
-            Contract.Requires(noPatterns == null || Contract.ForAll(noPatterns, np => np != null));
+            Debug.Assert(noPatterns == null || noPatterns.All(np => np != null));
-            Contract.Requires(bound == null || Contract.ForAll(bound, n => n != null));
+            Debug.Assert(bound == null || bound.All(n => n != null));
 
             Context.CheckContextMatch<Expr>(noPatterns);
             Context.CheckContextMatch<Pattern>(patterns);
@@ -246,7 +239,7 @@ namespace Microsoft.Z3
         }
 
 
-        internal Quantifier(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal Quantifier(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
 #if DEBUG
         internal override void CheckNativeObject(IntPtr obj)

src/api/dotnet/RatNum.cs

@@ -16,8 +16,8 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 #if !FRAMEWORK_LT_4
 using System.Numerics;
@@ -28,7 +28,6 @@ namespace Microsoft.Z3
     /// <summary>
     /// Rational Numerals
     /// </summary>
-    [ContractVerification(true)]
     public class RatNum : RealExpr
     {
         /// <summary>
@@ -38,7 +37,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<IntNum>() != null);
 
                 return new IntNum(Context, Native.Z3_get_numerator(Context.nCtx, NativeObject));
             }
@@ -51,7 +49,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<IntNum>() != null);
 
                 return new IntNum(Context, Native.Z3_get_denominator(Context.nCtx, NativeObject));
             }
@@ -92,6 +89,14 @@ namespace Microsoft.Z3
             return Native.Z3_get_numeral_decimal_string(Context.nCtx, NativeObject, precision);
         }
 
+        /// <summary>
+        /// Returns a double representing the value.
+        /// </summary>
+        public double Double
+        {
+            get { return Native.Z3_get_numeral_double(Context.nCtx, NativeObject); }
+        }
+
         /// <summary>
         /// Returns a string representation of the numeral.
         /// </summary>        
@@ -104,7 +109,7 @@ namespace Microsoft.Z3
         internal RatNum(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/ReExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal ReExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/ReSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -31,12 +31,12 @@ namespace Microsoft.Z3
         internal ReSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal ReSort(Context ctx)
             : base(ctx, Native.Z3_mk_int_sort(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/RealExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal RealExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/RealSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -31,12 +31,12 @@ namespace Microsoft.Z3
         internal RealSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal RealSort(Context ctx)
             : base(ctx, Native.Z3_mk_real_sort(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/RelationSort.cs

@@ -17,15 +17,14 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Relation sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class RelationSort : Sort
     {
         /// <summary>
@@ -43,7 +42,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Sort[]>() != null);
 
                 if (m_columnSorts != null)
                     return m_columnSorts;
@@ -62,7 +60,7 @@ namespace Microsoft.Z3
         internal RelationSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/SeqExpr.cs

@@ -16,12 +16,12 @@ Author:
 Notes:
     
 --*/
+using System.Diagnostics;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -35,7 +35,7 @@ namespace Microsoft.Z3
         internal SeqExpr(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/SeqSort.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -31,12 +31,12 @@ namespace Microsoft.Z3
         internal SeqSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal SeqSort(Context ctx)
             : base(ctx, Native.Z3_mk_int_sort(ctx.nCtx))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         #endregion
     }

src/api/dotnet/SetSort.cs

@@ -17,28 +17,27 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Set sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class SetSort : Sort
     {
         #region Internal
         internal SetSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal SetSort(Context ctx, Sort ty)
             : base(ctx, Native.Z3_mk_set_sort(ctx.nCtx, ty.NativeObject))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(ty != null);
+            Debug.Assert(ty != null);
         }
         #endregion
     }

src/api/dotnet/Solver.cs

@@ -18,16 +18,15 @@ Notes:
 --*/
 
 using System;
+using System.Diagnostics;
 using System.Linq;
 using System.Collections.Generic;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Solvers.
     /// </summary>
-    [ContractVerification(true)]
     public class Solver : Z3Object
     {
         /// <summary>
@@ -37,7 +36,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<string>() != null);
 
                 return Native.Z3_solver_get_help(Context.nCtx, NativeObject);
             }
@@ -50,7 +48,7 @@ namespace Microsoft.Z3
         {
             set
             {
-                Contract.Requires(value != null);
+                Debug.Assert(value != null);
 
                 Context.CheckContextMatch(value);
                 Native.Z3_solver_set_params(Context.nCtx, NativeObject, value.NativeObject);
@@ -152,8 +150,8 @@ namespace Microsoft.Z3
         /// </summary>        
         public void Assert(params BoolExpr[] constraints)
         {
-            Contract.Requires(constraints != null);
+            Debug.Assert(constraints != null);
-            Contract.Requires(Contract.ForAll(constraints, c => c != null));
+            Debug.Assert(constraints.All(c => c != null));
 
             Context.CheckContextMatch<BoolExpr>(constraints);
             foreach (BoolExpr a in constraints)
@@ -191,9 +189,9 @@ namespace Microsoft.Z3
         /// </remarks>        
         public void AssertAndTrack(BoolExpr[] constraints, BoolExpr[] ps)
         {
-            Contract.Requires(constraints != null);
+            Debug.Assert(constraints != null);
-            Contract.Requires(Contract.ForAll(constraints, c => c != null));
+            Debug.Assert(constraints.All(c => c != null));
-            Contract.Requires(Contract.ForAll(ps, c => c != null));
+            Debug.Assert(ps.All(c => c != null));
             Context.CheckContextMatch<BoolExpr>(constraints);
             Context.CheckContextMatch<BoolExpr>(ps);
             if (constraints.Length != ps.Length)
@@ -216,8 +214,8 @@ namespace Microsoft.Z3
         /// </remarks>        
         public void AssertAndTrack(BoolExpr constraint, BoolExpr p)
         {
-            Contract.Requires(constraint != null);
+            Debug.Assert(constraint != null);
-            Contract.Requires(p != null);
+            Debug.Assert(p != null);
             Context.CheckContextMatch(constraint);
             Context.CheckContextMatch(p);
                         
@@ -259,7 +257,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr[]>() != null);
 
                 ASTVector assertions = new ASTVector(Context, Native.Z3_solver_get_assertions(Context.nCtx, NativeObject));
                 return assertions.ToBoolExprArray();
@@ -273,7 +270,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<BoolExpr[]>() != null);
 
                 ASTVector assertions = new ASTVector(Context, Native.Z3_solver_get_units(Context.nCtx, NativeObject));
                 return assertions.ToBoolExprArray();
@@ -394,7 +390,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Expr[]>() != null);
 
                 ASTVector core = new ASTVector(Context, Native.Z3_solver_get_unsat_core(Context.nCtx, NativeObject));                
                 return core.ToBoolExprArray();
@@ -408,7 +403,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<string>() != null);
 
                 return Native.Z3_solver_get_reason_unknown(Context.nCtx, NativeObject);
             }
@@ -455,8 +449,7 @@ namespace Microsoft.Z3
         /// </summary>
         public Solver Translate(Context ctx) 
         {
-             Contract.Requires(ctx != null);
+             Debug.Assert(ctx != null);
-             Contract.Ensures(Contract.Result<Solver>() != null);
              return new Solver(ctx, Native.Z3_solver_translate(Context.nCtx, NativeObject, ctx.nCtx));
         }
 
@@ -475,7 +468,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Statistics>() != null);
 
                 return new Statistics(Context, Native.Z3_solver_get_statistics(Context.nCtx, NativeObject));
             }
@@ -493,7 +485,7 @@ namespace Microsoft.Z3
         internal Solver(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
             this.BacktrackLevel = uint.MaxValue;
         }
 

src/api/dotnet/Sort.cs

@@ -17,15 +17,14 @@ Notes:
 
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// The Sort class implements type information for ASTs.
     /// </summary>
-    [ContractVerification(true)]
     public class Sort : AST
     {
         /// <summary>
@@ -100,7 +99,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Symbol>() != null);
                 return Symbol.Create(Context, Native.Z3_get_sort_name(Context.nCtx, NativeObject));
             }
         }
@@ -127,7 +125,7 @@ namespace Microsoft.Z3
         /// <summary>
         /// Sort constructor
         /// </summary>
-        internal Sort(Context ctx, IntPtr obj) : base(ctx, obj) { Contract.Requires(ctx != null); }
+        internal Sort(Context ctx, IntPtr obj) : base(ctx, obj) { Debug.Assert(ctx != null); }
 
 #if DEBUG
         internal override void CheckNativeObject(IntPtr obj)
@@ -138,11 +136,9 @@ namespace Microsoft.Z3
         }
 #endif
 
-        [ContractVerification(true)]
         new internal static Sort Create(Context ctx, IntPtr obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Ensures(Contract.Result<Sort>() != null);
 
             switch ((Z3_sort_kind)Native.Z3_get_sort_kind(ctx.nCtx, obj))
             {

src/api/dotnet/Statistics.cs

@@ -18,14 +18,14 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
+
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Objects of this class track statistical information about solvers. 
     /// </summary>
-    [ContractVerification(true)]
     public class Statistics : Z3Object
     {
         /// <summary>
@@ -62,7 +62,6 @@ namespace Microsoft.Z3
             {
                 get
                 {
-                    Contract.Ensures(Contract.Result<string>() != null);
 
                     if (IsUInt)
                         return m_uint.ToString();
@@ -124,9 +123,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Entry[]>() != null);
-                Contract.Ensures(Contract.Result<Entry[]>().Length == this.Size);
-                Contract.Ensures(Contract.ForAll(0, Contract.Result<Entry[]>().Length, j => Contract.Result<Entry[]>()[j] != null));
 
                 uint n = Size;
                 Entry[] res = new Entry[n];
@@ -153,7 +149,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<string[]>() != null);
 
                 uint n = Size;
                 string[] res = new string[n];
@@ -184,7 +179,7 @@ namespace Microsoft.Z3
         internal Statistics(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal class DecRefQueue : IDecRefQueue

src/api/dotnet/Status.cs

@@ -17,6 +17,7 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
 
 namespace Microsoft.Z3

src/api/dotnet/StringSymbol.cs

@@ -18,8 +18,8 @@ Notes:
 --*/
 
 using System;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -27,7 +27,6 @@ namespace Microsoft.Z3
     /// <summary>
     /// Named symbols
     /// </summary>
-    [ContractVerification(true)]
     public class StringSymbol : Symbol
     {
         /// <summary>
@@ -38,7 +37,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<string>() != null);
 
                 if (!IsStringSymbol())
                     throw new Z3Exception("String requested from non-String symbol");
@@ -50,13 +48,13 @@ namespace Microsoft.Z3
         internal StringSymbol(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal StringSymbol(Context ctx, string s)
             : base(ctx, Native.Z3_mk_string_symbol(ctx.nCtx, s))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
 #if DEBUG

src/api/dotnet/Symbol.cs

@@ -18,15 +18,14 @@ Notes:
 --*/
 
 using System;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Symbols are used to name several term and type constructors.
     /// </summary>
-    [ContractVerification(true)]
     public class Symbol : Z3Object
     {
         /// <summary>
@@ -84,7 +83,7 @@ namespace Microsoft.Z3
         /// </summary>
         public static bool operator !=(Symbol s1, Symbol s2)
         {
-            return !(s1.NativeObject == s2.NativeObject);
+            return !(s1 == s2);
         }
 
         /// <summary>
@@ -113,13 +112,12 @@ namespace Microsoft.Z3
         /// </summary>
         internal protected Symbol(Context ctx, IntPtr obj) : base(ctx, obj) 
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         internal static Symbol Create(Context ctx, IntPtr obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Ensures(Contract.Result<Symbol>() != null);
 
             switch ((Z3_symbol_kind)Native.Z3_get_symbol_kind(ctx.nCtx, obj))
             {

src/api/dotnet/Tactic.cs

@@ -18,7 +18,7 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
 
 namespace Microsoft.Z3
 {
@@ -28,7 +28,6 @@ namespace Microsoft.Z3
     /// and <c>Context.TacticNames</c>.
     /// It may also be obtained using the command <c>(help-tactic)</c> in the SMT 2.0 front-end.
     /// </summary>
-    [ContractVerification(true)]
     public class Tactic : Z3Object
     {
         /// <summary>
@@ -38,7 +37,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<string>() != null);
 
                 return Native.Z3_tactic_get_help(Context.nCtx, NativeObject);
             }
@@ -59,8 +57,7 @@ namespace Microsoft.Z3
         /// </summary>
         public ApplyResult Apply(Goal g, Params p = null)
         {
-            Contract.Requires(g != null);
+            Debug.Assert(g != null);
-            Contract.Ensures(Contract.Result<ApplyResult>() != null);
 
             Context.CheckContextMatch(g);
             if (p == null)
@@ -79,8 +76,7 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Requires(g != null);
+                Debug.Assert(g != null);
-                Contract.Ensures(Contract.Result<ApplyResult>() != null);
 
                 return Apply(g);
             }
@@ -94,7 +90,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<Solver>() != null);
 
                 return Context.MkSolver(this);
             }
@@ -104,12 +99,12 @@ namespace Microsoft.Z3
         internal Tactic(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal Tactic(Context ctx, string name)
             : base(ctx, Native.Z3_mk_tactic(ctx.nCtx, name))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
 
         /// <summary>

src/api/dotnet/TupleSort.cs

@@ -18,14 +18,13 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
 
 namespace Microsoft.Z3
 {
     /// <summary>
     /// Tuple sorts.
     /// </summary>
-    [ContractVerification(true)]
     public class TupleSort : Sort
     {
         /// <summary>
@@ -35,7 +34,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl>() != null);
 
                 return new FuncDecl(Context, Native.Z3_get_tuple_sort_mk_decl(Context.nCtx, NativeObject));
             }
@@ -56,7 +54,6 @@ namespace Microsoft.Z3
         {
             get
             {
-                Contract.Ensures(Contract.Result<FuncDecl[]>() != null);
 
                 uint n = NumFields;
                 FuncDecl[] res = new FuncDecl[n];
@@ -70,8 +67,8 @@ namespace Microsoft.Z3
         internal TupleSort(Context ctx, Symbol name, uint numFields, Symbol[] fieldNames, Sort[] fieldSorts)
             : base(ctx, IntPtr.Zero)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(name != null);
+            Debug.Assert(name != null);
 
             IntPtr t = IntPtr.Zero;
             IntPtr[] f = new IntPtr[numFields];

src/api/dotnet/UninterpretedSort.cs

@@ -18,7 +18,7 @@ Notes:
 --*/
 
 using System;
-using System.Diagnostics.Contracts;
+using System.Diagnostics;
 
 namespace Microsoft.Z3
 {
@@ -31,13 +31,13 @@ namespace Microsoft.Z3
         internal UninterpretedSort(Context ctx, IntPtr obj)
             : base(ctx, obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
         }
         internal UninterpretedSort(Context ctx, Symbol s)
             : base(ctx, Native.Z3_mk_uninterpreted_sort(ctx.nCtx, s.NativeObject))
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
-            Contract.Requires(s != null);
+            Debug.Assert(s != null);
         }
         #endregion
     }

src/api/dotnet/Version.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 
 namespace Microsoft.Z3
 {
@@ -26,7 +26,6 @@ namespace Microsoft.Z3
     /// Version information.
     /// </summary>
     /// <remarks>Note that this class is static.</remarks>
-    [ContractVerification(true)]
     public static class Version
     {
         static Version() { }
@@ -99,7 +98,6 @@ namespace Microsoft.Z3
         /// </summary>
         new public static string ToString()
         {
-            Contract.Ensures(Contract.Result<string>() != null);
 
             uint major = 0, minor = 0, build = 0, revision = 0;
             Native.Z3_get_version(ref major, ref minor, ref build, ref revision);

src/api/dotnet/Z3Exception.cs

@@ -17,6 +17,7 @@ Notes:
 
 --*/
 
+using System.Diagnostics;
 using System;
 
 namespace Microsoft.Z3

src/api/dotnet/Z3Object.cs

@@ -17,8 +17,8 @@ Notes:
     
 --*/
 
+using System.Diagnostics;
 using System;
-using System.Diagnostics.Contracts;
 using System.Threading;
 using System.Collections.Generic;
 using System.Linq;
@@ -29,7 +29,6 @@ namespace Microsoft.Z3
     /// Internal base class for interfacing with native Z3 objects.
     /// Should not be used externally.
     /// </summary>
-    [ContractVerification(true)]
     public class Z3Object : IDisposable
     {
         /// <summary>
@@ -63,10 +62,9 @@ namespace Microsoft.Z3
 
         #region Object Invariant
         
-        [ContractInvariantMethod]
         private void ObjectInvariant()
         {
-            Contract.Invariant(this.m_ctx != null);
+            Debug.Assert(this.m_ctx != null);
         }
 
         #endregion
@@ -77,7 +75,7 @@ namespace Microsoft.Z3
 
         internal Z3Object(Context ctx)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
 
             Interlocked.Increment(ref ctx.refCount);
             m_ctx = ctx;
@@ -85,7 +83,7 @@ namespace Microsoft.Z3
 
         internal Z3Object(Context ctx, IntPtr obj)
         {
-            Contract.Requires(ctx != null);
+            Debug.Assert(ctx != null);
 
             Interlocked.Increment(ref ctx.refCount);
             m_ctx = ctx;
@@ -119,16 +117,12 @@ namespace Microsoft.Z3
         {
             get 
             {
-                Contract.Ensures(Contract.Result<Context>() != null);
                 return m_ctx; 
             }            
         }
 
-        [Pure]
         internal static IntPtr[] ArrayToNative(Z3Object[] a)
         {
-            Contract.Ensures(a == null || Contract.Result<IntPtr[]>() != null);
-            Contract.Ensures(a == null || Contract.Result<IntPtr[]>().Length == a.Length);
 
             if (a == null) return null;
             IntPtr[] an = new IntPtr[a.Length];
@@ -137,11 +131,8 @@ namespace Microsoft.Z3
             return an;
         }
 
-        [Pure]
         internal static IntPtr[] EnumToNative<T>(IEnumerable<T> a) where T : Z3Object
         {
-            Contract.Ensures(a == null || Contract.Result<IntPtr[]>() != null);
-            Contract.Ensures(a == null || Contract.Result<IntPtr[]>().Length == a.Count());
 
             if (a == null) return null;
             IntPtr[] an = new IntPtr[a.Count()];
@@ -154,7 +145,6 @@ namespace Microsoft.Z3
             return an;
         }
 
-        [Pure]
         internal static uint ArrayLength(Z3Object[] a)
         {
             return (a == null)?0:(uint)a.Length;

src/api/dotnet/core/DummyContracts.cs

@@ -1,65 +0,0 @@
-/*++
-Copyright (<c>) 2016 Microsoft Corporation
-
-Module Name:
-
-    Contracts.cs
-
-Abstract:
-
-    Z3 Managed API: Dummy Code Contracts class for .NET
-    frameworks that don't support them (e.g., CoreCLR).
-
-Author:
-
-    Christoph Wintersteiger (cwinter) 2016-10-06
-
-Notes:
-
---*/
-
-namespace System.Diagnostics.Contracts
-{
-    public class ContractClass : Attribute
-    {
-        public ContractClass(Type t) { }
-    }
-
-    public class ContractClassFor : Attribute
-    {
-        public ContractClassFor(Type t) { }
-    }
-
-    public class ContractInvariantMethod : Attribute
-    {
-        public ContractInvariantMethod() { }
-    }
-
-    public class ContractVerification : Attribute
-    {
-        public ContractVerification(bool b) { }
-    }
-
-    public class Pure : Attribute { }
-
-    public static class Contract
-    {
-        [Conditional("false")]
-        public static void Ensures(bool b) { }
-        [Conditional("false")]
-        public static void Requires(bool b) { }
-        [Conditional("false")]
-        public static void Assume(bool b, string msg) { }
-        [Conditional("false")]
-        public static void Assert(bool b) { }
-        public static bool ForAll(bool b) { return true; }
-        public static bool ForAll(Object c, Func<Object, bool> p) { return true; }
-        public static bool ForAll(int from, int to, Predicate<int> p) { return true; }
-        [Conditional("false")]
-        public static void Invariant(bool b) { }
-        public static T[] Result<T>() { return new T[1]; }
-        [Conditional("false")]
-        public static void EndContractBlock() { }
-        public static T ValueAtReturn<T>(out T v) { T[] t = new T[1]; v = t[0]; return v; }
-    }
-}

src/api/dotnet/core/README.txt

@@ -6,4 +6,10 @@ functions, so that the API will compile, but not perform any contract
 checking. To build this using .NET core, run (in this directory):
 
 dotnet restore
-dotnet build project.json
+dotnet build core.csproj -c Release
+
+If you are building with the cmake system, you should first
+copy over files that are produced by the compiler into
+this directory. You need to copy over Native.cs and Enumeration.cs
+
+-- good luck!

src/api/dotnet/core/core.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp1.0</TargetFramework>
+    <DefineConstants>$(DefineConstants);DOTNET_CORE</DefineConstants>
+    <DebugType>portable</DebugType>
+    <AssemblyName>Microsoft.Z3</AssemblyName>
+    <OutputType>Library</OutputType>
+    <PackageId>core</PackageId>
+    <PackageTargetFallback>$(PackageTargetFallback);dnxcore50</PackageTargetFallback>
+    <RuntimeFrameworkVersion>1.0.4</RuntimeFrameworkVersion>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="..\*.cs" Exclude="bin\**;obj\**;**\*.xproj;packages\**" />
+  </ItemGroup>
+
+</Project>

src/api/python/z3/z3util.py

@@ -199,7 +199,7 @@ def prove(claim,assume=None,verbose=0):
     >>> r,m = prove(True,assume=And(x,Not(x)),verbose=0)
     Traceback (most recent call last):
     ...
-    AssertionError: Assumption is alway False!
+    AssertionError: Assumption is always False!
 
     >>> r,m = prove(Implies(x,x),assume=y,verbose=2); r,model_str(m,as_str=False)
     assume: 
@@ -238,7 +238,7 @@ def prove(claim,assume=None,verbose=0):
             is_proved,_ = prove(Not(assume))
 
             def _f():
-                emsg = "Assumption is alway False!"
+                emsg = "Assumption is always False!"
                 if verbose >= 2:
                     emsg = "{}\n{}".format(assume,emsg)
                 return emsg

src/api/z3_api.h

@@ -3772,7 +3772,7 @@ extern "C" {
         );
 
     /**
-       \brief Create a lambda expression. It taks an expression \c body that contains bound variables 
+       \brief Create a lambda expression. It takes an expression \c body that contains bound variables
        of the same sorts as the sorts listed in the array \c sorts. The bound variables are de-Bruijn indices created
        using #Z3_mk_bound. The array \c decl_names contains the names that the quantified formula uses for the
        bound variables. Z3 applies the convention that the last element in the \c decl_names and \c sorts array
@@ -4438,6 +4438,15 @@ extern "C" {
     */
     Z3_string Z3_API Z3_get_numeral_decimal_string(Z3_context c, Z3_ast a, unsigned precision);
 
+    /**
+       \brief Return numeral as a double.
+
+       \pre Z3_get_ast_kind(c, a) == Z3_NUMERAL_AST || Z3_is_algebraic_number(c, a)
+
+       def_API('Z3_get_numeral_double', DOUBLE, (_in(CONTEXT), _in(AST)))
+    */
+    double Z3_API Z3_get_numeral_double(Z3_context c, Z3_ast a);
+
     /**
        \brief Return the numerator (as a numeral AST) of a numeral AST of sort Real.
 
@@ -4600,7 +4609,7 @@ extern "C" {
     Z3_bool Z3_API Z3_is_quantifier_exists(Z3_context c, Z3_ast a);
 
     /**
-       \brief Determine if ast is a lambda expresion.
+       \brief Determine if ast is a lambda expression.
 
        \pre Z3_get_ast_kind(a) == Z3_QUANTIFIER_AST
 
@@ -5987,7 +5996,7 @@ extern "C" {
     Z3_solver Z3_API Z3_solver_translate(Z3_context source, Z3_solver s, Z3_context target);
 
     /**
-       \brief Ad-hoc method for importing model convertion from solver.
+       \brief Ad-hoc method for importing model conversion from solver.
        
        def_API('Z3_solver_import_model_converter', VOID, (_in(CONTEXT), _in(SOLVER), _in(SOLVER)))
      */
@@ -6206,7 +6215,7 @@ extern "C" {
        The third argument is a vector of variables that may be used for cubing.
        The contents of the vector is only used in the first call. The initial list of variables
        is used in subsequent calls until it returns the unsatisfiable cube. 
-       The vector is modified to contain a set of Autarky variables that occor in clauses that
+       The vector is modified to contain a set of Autarky variables that occur in clauses that
        are affected by the (last literal in the) cube. These variables could be used by a different
        cuber (on a different solver object) for further recursive cubing. 
 

src/ast/ast_util.h

@@ -123,7 +123,7 @@ inline expr_ref mk_or(expr_ref_vector const& args) { return expr_ref(mk_or(args.
 
 /**
    Return a          if arg = (not a)
-   Retur (not arg)   otherwise
+   Return (not arg)  otherwise
  */
 expr * mk_not(ast_manager & m, expr * arg);
 

src/ast/fpa/fpa2bv_rewriter.cpp

@@ -31,7 +31,7 @@ fpa2bv_rewriter_cfg::fpa2bv_rewriter_cfg(ast_manager & m, fpa2bv_converter & c,
     m_bindings(m)
 {
     updt_params(p);
-    // We need to make sure that the mananger has the BV plugin loaded.
+    // We need to make sure that the manager has the BV plugin loaded.
     symbol s_bv("bv");
     if (!m_manager.has_plugin(s_bv))
         m_manager.register_plugin(s_bv, alloc(bv_decl_plugin));