adding dump facility for cancelation #2095, easing dimacs in/out

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/ast/CMakeLists.txt

@@ -17,6 +17,7 @@ z3_add_component(ast
     csp_decl_plugin.cpp
     datatype_decl_plugin.cpp
     decl_collector.cpp
+    display_dimacs.cpp
     dl_decl_plugin.cpp
     expr2polynomial.cpp
     expr2var.cpp

src/ast/display_dimacs.cpp

@@ -0,0 +1,81 @@
+/*++
+Copyright (c) 2019 Microsoft Corporation
+
+Module Name:
+
+    display_dimacs.h
+
+Abstract:
+
+    Display expressions in DIMACS format.
+    
+Author:
+
+    Nikolaj Bjorner (nbjorner0 2019-01-24
+
+Revision History:
+
+--*/
+
+#include "ast.h"
+#include "display_dimacs.h"
+
+std::ostream& display_dimacs(std::ostream& out, expr_ref_vector const& fmls) {
+    ast_manager& m = fmls.m();
+    unsigned_vector expr2var;
+    ptr_vector<expr> exprs;
+    unsigned num_vars = 0;
+    unsigned num_cls  = fmls.size();
+    for (expr * f : fmls) {
+        unsigned num_lits;
+        expr * const * lits;
+        if (m.is_or(f)) {
+            num_lits = to_app(f)->get_num_args();
+            lits     = to_app(f)->get_args();
+        }
+        else {
+            num_lits = 1;
+            lits     = &f;
+        }
+        for (unsigned j = 0; j < num_lits; j++) {
+            expr * l = lits[j];
+            if (m.is_not(l))
+                l = to_app(l)->get_arg(0);
+            if (expr2var.get(l->get_id(), UINT_MAX) == UINT_MAX) {
+                num_vars++;
+                expr2var.setx(l->get_id(), num_vars, UINT_MAX);
+                exprs.setx(l->get_id(), l, nullptr);
+            }
+        }
+    }
+    out << "p cnf " << num_vars << " " << num_cls << "\n";
+    for (expr* f : fmls) {
+        unsigned num_lits;
+        expr * const * lits;
+        if (m.is_or(f)) {
+            num_lits = to_app(f)->get_num_args();
+            lits     = to_app(f)->get_args();
+        }
+        else {
+            num_lits = 1;
+            lits     = &f;
+        }
+        for (unsigned j = 0; j < num_lits; j++) {
+            expr * l = lits[j];
+            if (m.is_not(l)) {
+                out << "-";
+                l = to_app(l)->get_arg(0);
+            }
+            SASSERT(exprs[l->get_id()]);
+            out << expr2var[l->get_id()] << " ";
+        }
+        out << "0\n";
+    }
+    for (expr* e : exprs) {
+        if (e && is_app(e)) {
+            symbol const& n = to_app(e)->get_decl()->get_name();
+            out << "c " << expr2var[e->get_id()] << " " << n << "\n";            
+        }
+    }
+    return out;
+}

src/ast/display_dimacs.h

@@ -0,0 +1,26 @@
+/*++
+Copyright (c) 2019 Microsoft Corporation
+
+Module Name:
+
+    display_dimacs.h
+
+Abstract:
+
+    Display expressions in DIMACS format.
+    
+Author:
+
+    Nikolaj Bjorner (nbjorner0 2019-01-24
+
+Revision History:
+
+--*/
+#ifndef DISPLAY_DIMACS_H_
+#define DISPLAY_DIMACS_H_
+
+#include "ast.h"
+
+std::ostream& display_dimacs(std::ostream& out, expr_ref_vector const& fmls);
+
+#endif /* DISPLAY_DIMACS_H__ */