Z3 sources

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

lib/elim_bounds.h

@@ -0,0 +1,69 @@
+/*++
+Copyright (c) 2006 Microsoft Corporation
+
+Module Name:
+
+    elim_bounds.h
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Leonardo de Moura (leonardo) 2008-06-28.
+
+Revision History:
+
+--*/
+#ifndef _ELIM_BOUNDS_H_
+#define _ELIM_BOUNDS_H_
+
+#include"ast.h"
+#include"arith_decl_plugin.h"
+#include"simplifier.h"
+
+/**
+   \brief Functor for eliminating irrelevant bounds in quantified formulas.
+   
+   Example:
+   (forall (x Int) (y Int) (or (not (>= y x) (not (>= x 0)) (= (select a x) 1))))
+
+   The bound (>= y x) is irrelevant and can be eliminated.
+
+   This can be easily proved by using Fourier-Motzkin elimination.
+
+   Limitations & Assumptions:
+   - It assumes the input formula was already simplified.
+   - It can only handle bounds in the diff-logic fragment.
+
+   \remark This operation is subsumed by Fourier-Motzkin elimination.
+*/
+class elim_bounds {
+    ast_manager &      m_manager;
+    arith_util         m_util;
+    bool is_bound(expr * n, var * & lower, var * & upper);
+    bool is_bound(expr * n);
+public:
+    elim_bounds(ast_manager & m);
+    void operator()(quantifier * q, expr_ref & r);
+};
+
+/**
+   \brief Functor for applying elim_bounds in all
+   universal quantifiers in an expression.
+
+   Assumption: the formula was already skolemized.
+*/
+class elim_bounds_star : public simplifier {
+protected:
+    elim_bounds  m_elim;
+    virtual bool visit_quantifier(quantifier * q);
+    virtual void reduce1_quantifier(quantifier * q);
+public:
+    elim_bounds_star(ast_manager & m):simplifier(m), m_elim(m) { enable_ac_support(false); }
+    virtual ~elim_bounds_star() {}
+};
+
+#endif /* _ELIM_BOUNDS_H_ */
+