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src/ast/rewriter/seq_eq_solver.cpp

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+/*++
+Copyright (c) 2011 Microsoft Corporation
+
+Module Name:
+
+    seq_eq_solver
+
+Abstract:
+
+    Solver-agnostic equality solving routines for sequences
+    
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2021-03-01
+
+--*/
+
+#include "ast/rewriter/seq_eq_solver.h"
+
+namespace seq {
+
+
+    bool eq_solver::solve(eq const& e, eq_ptr& r) {
+        if (solve_itos1(e, r))
+            return true;
+        if (solve_itos2(e, r))
+            return true;
+
+        return false;
+    }
+
+    void eq_solver::add_consequence(expr_ref const& a) {
+        m_clause.reset();
+        m_clause.push_back(a);
+        m_add_consequence(true, m_clause);
+    }
+
+    void eq_solver::add_consequence(expr_ref const& a, expr_ref const& b) {
+        m_clause.reset();
+        m_clause.push_back(a);
+        m_clause.push_back(b);
+        m_add_consequence(true, m_clause);
+    }
+
+    /**
+     * from_int(s) == from_int(t)
+     * --------------------------
+     * s = t or (s < 0 and t < 0)
+     */
+        
+    bool eq_solver::match_itos1(eq const& e, expr*& a, expr*& b) {
+        return 
+            e.ls.size() == 1 && e.rs.size() == 1 && 
+            seq.str.is_itos(e.ls[0], a) && seq.str.is_itos(e.rs[0], b);
+    }
+
+    bool eq_solver::solve_itos1(eq const& e, eq_ptr& r) {
+        expr* s = nullptr, *t = nullptr;
+        if (!match_itos1(e, s, t))
+            return false;
+        r = nullptr;
+        expr_ref eq = mk_eq(s, t);
+        add_consequence(eq, mk_le(s, -1));
+        add_consequence(eq, mk_le(t, -1));
+        return true;
+    }
+
+    /**
+     * from_int(s) == ""
+     * -----------------
+     *       s < 0
+     */
+    
+    bool eq_solver::match_itos2(eq const& e, expr*& s) {
+        if (e.ls.size() == 1 && e.rs.empty() && seq.str.is_itos(e.ls[0], s))
+            return true;
+        if (e.rs.size() == 1 && e.ls.empty() && seq.str.is_itos(e.rs[0], s))
+            return true;
+        return false;
+    }
+
+    bool eq_solver::solve_itos2(eq const& e, eq_ptr& r) {
+        expr* s = nullptr;
+        if (!match_itos2(e, s))
+            return false;
+        r = nullptr;
+        add_consequence(mk_le(s, -1));
+        return true;
+    }
+
+};
+