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Add Java APIs for polymorphic datatypes (#8438)

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* Initial plan

* Add Java APIs for polymorphic datatypes and type variables

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Fix code review issue and add documentation

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

* Add TypeVarSort.java to CMakeLists.txt for Java bindings

The CMake build was failing because TypeVarSort.java was not included in the Z3_JAVA_JAR_SOURCE_FILES list in src/api/java/CMakeLists.txt. Added it in alphabetical order between TupleSort.java and UninterpretedSort.java.

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
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138
examples/java/PolymorphicDatatypeExample.java Normal file
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/**
Copyright (c) 2024 Microsoft Corporation
Module Name:
PolymorphicDatatypeExample.java
Abstract:
Example demonstrating the use of polymorphic (parametric) datatypes in Z3's Java API.
This example creates a polymorphic List[T] datatype and demonstrates its usage.
Author:
GitHub Copilot 2024-01-30
Notes:
**/
import com.microsoft.z3.*;
public class PolymorphicDatatypeExample {
/**
* Create a polymorphic List[T] datatype.
* This is equivalent to:
* datatype List[T] = nil | cons(head: T, tail: List[T])
*/
static void polymorphicListExample(Context ctx) {
System.out.println("PolymorphicListExample");
// Create a type variable T
TypeVarSort T = ctx.mkTypeVariable("T");
// Create constructors for the List[T] datatype
// nil constructor (no arguments)
Constructor<Object> nil = ctx.mkConstructor("nil", "is_nil", null, null, null);
// cons constructor with head:T and tail:List[T]
String[] fieldNames = new String[] { "head", "tail" };
Sort[] fieldSorts = new Sort[] { T, null }; // null means recursive reference
int[] sortRefs = new int[] { 0, 0 }; // both refer to the datatype being defined
Constructor<Object> cons = ctx.mkConstructor("cons", "is_cons", fieldNames, fieldSorts, sortRefs);
// Create the polymorphic List[T] datatype
Constructor<Object>[] constructors = new Constructor[] { nil, cons };
DatatypeSort<Object> listSort = ctx.mkPolymorphicDatatypeSort("List", new Sort[]{T}, constructors);
System.out.println("Created polymorphic List datatype: " + listSort);
// Get the constructor and accessor functions
FuncDecl<?>[] listConstructors = listSort.getConstructors();
FuncDecl<?> nilDecl = listConstructors[0];
FuncDecl<?> consDecl = listConstructors[1];
System.out.println("nil constructor: " + nilDecl);
System.out.println("cons constructor: " + consDecl);
// Get accessors
FuncDecl<?>[][] accessors = listSort.getAccessors();
if (accessors.length > 1 && accessors[1].length == 2) {
FuncDecl<?> headAccessor = accessors[1][0];
FuncDecl<?> tailAccessor = accessors[1][1];
System.out.println("head accessor: " + headAccessor);
System.out.println("tail accessor: " + tailAccessor);
}
System.out.println("Polymorphic List example completed successfully!");
}
/**
* Create a polymorphic Option[T] datatype (like Maybe in Haskell).
* This is equivalent to:
* datatype Option[T] = none | some(value: T)
*/
static void polymorphicOptionExample(Context ctx) {
System.out.println("\nPolymorphicOptionExample");
// Create a type variable T
TypeVarSort T = ctx.mkTypeVariable("T");
// Create constructors for Option[T]
Constructor<Object> none = ctx.mkConstructor("none", "is_none", null, null, null);
String[] fieldNames = new String[] { "value" };
Sort[] fieldSorts = new Sort[] { T };
int[] sortRefs = new int[] { 0 }; // not used since T is not recursive
Constructor<Object> some = ctx.mkConstructor("some", "is_some", fieldNames, fieldSorts, sortRefs);
// Create the polymorphic Option[T] datatype
Constructor<Object>[] constructors = new Constructor[] { none, some };
DatatypeSort<Object> optionSort = ctx.mkPolymorphicDatatypeSort("Option", new Sort[]{T}, constructors);
System.out.println("Created polymorphic Option datatype: " + optionSort);
FuncDecl<?>[] optionConstructors = optionSort.getConstructors();
System.out.println("none constructor: " + optionConstructors[0]);
System.out.println("some constructor: " + optionConstructors[1]);
System.out.println("Polymorphic Option example completed successfully!");
}
/**
* Demonstrate type variables can be created with different names
*/
static void typeVariableExample(Context ctx) {
System.out.println("\nTypeVariableExample");
TypeVarSort T = ctx.mkTypeVariable("T");
TypeVarSort U = ctx.mkTypeVariable("U");
TypeVarSort V = ctx.mkTypeVariable("V");
System.out.println("Created type variable T: " + T);
System.out.println("Created type variable U: " + U);
System.out.println("Created type variable V: " + V);
// Type variables can be used as sort parameters
System.out.println("Type variables can be used as parameters for polymorphic datatypes");
}
public static void main(String[] args) {
try {
// Use try-with-resources to ensure proper cleanup
try (Context ctx = new Context()) {
typeVariableExample(ctx);
polymorphicListExample(ctx);
polymorphicOptionExample(ctx);
System.out.println("\n=== All polymorphic datatype examples completed successfully! ===");
}
} catch (Exception e) {
System.err.println("Error: " + e.getMessage());
e.printStackTrace();
System.exit(1);
}
}
}

42
examples/java/README
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@ -1,5 +1,13 @@
A small example using the Z3 Java bindings.
## Examples
- **JavaExample.java** - General examples demonstrating various Z3 features
- **JavaGenericExample.java** - Examples using generic Z3 types
- **PolymorphicDatatypeExample.java** - Examples of parametric/polymorphic datatypes with type variables
- **SeqOperationsExample.java** - Examples of sequence operations
- **RCFExample.java** - Examples using real closed fields
## IDE Setup
For detailed instructions on setting up Z3 Java bindings in Eclipse, IntelliJ IDEA,
@ -26,3 +34,37 @@ In certain environments, depending on the developing process, the Z3 library is
To disable the automated loading process, the user can set the environment variable "z3.skipLibraryLoad=true".
In that case, the calling application should directly load the corresponding libraries before any interaction with Z3.
## Polymorphic Datatypes
Z3's Java API now supports polymorphic (parametric) datatypes, similar to generic types in Java or templates in C++.
These allow you to define datatypes that are parameterized by type variables.
### Creating Type Variables
```java
Context ctx = new Context();
TypeVarSort T = ctx.mkTypeVariable("T");
TypeVarSort U = ctx.mkTypeVariable("U");
```
### Creating Polymorphic Datatypes
Example: Polymorphic List[T]
```java
// Create type variable
TypeVarSort T = ctx.mkTypeVariable("T");
// Define constructors
Constructor<Object> nil = ctx.mkConstructor("nil", "is_nil", null, null, null);
Constructor<Object> cons = ctx.mkConstructor("cons", "is_cons",
new String[]{"head", "tail"},
new Sort[]{T, null}, // null means recursive reference to List[T]
new int[]{0, 0});
// Create the polymorphic datatype
DatatypeSort<Object> listSort = ctx.mkPolymorphicDatatypeSort("List",
new Sort[]{T}, new Constructor[]{nil, cons});
```
See `PolymorphicDatatypeExample.java` for complete working examples.