preparing handling of arrays/quantifiers, fix cover-related bugs reported by Arie

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

src/muz_qe/equiv_proof_converter.h

@@ -0,0 +1,58 @@
+/*++
+Copyright (c) 2012 Microsoft Corporation
+
+Module Name:
+
+    equiv_proof_converter.h
+
+Abstract:
+
+    Proof converter that applies equivalence rule to leaves.
+
+    Given a proof P with occurrences of [asserted fml] 
+    replace [asserted fml] by a proof of the form
+    [mp [asserted fml'] [~ fml fml']]
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2012-11-23
+
+Revision History:  
+
+--*/
+
+#ifndef _EQUIV_PROOF_CONVERTER_H_
+#define _EQUIV_PROOF_CONVERTER_H_
+
+#include "replace_proof_converter.h"
+
+class equiv_proof_converter : public proof_converter {
+    ast_manager&            m;
+    replace_proof_converter m_replace;
+public:
+
+    equiv_proof_converter(ast_manager& m): m(m), m_replace(m) {}
+
+    virtual ~equiv_proof_converter() {}
+
+    virtual void operator()(ast_manager & m, unsigned num_source, proof * const * source, proof_ref & result) {
+        m_replace(m, num_source, source, result);
+    }
+
+    virtual proof_converter * translate(ast_translation & translator) {
+        return m_replace.translate(translator);
+    }
+
+    void insert(expr* fml1, expr* fml2) {
+        proof_ref p1(m), p2(m), p3(m);
+        p1 = m.mk_asserted(fml1);
+        p2 = m.mk_rewrite(fml1, fml2);
+        p3 = m.mk_modus_ponens(p1, p2);
+        m_replace.insert(p3);
+    }
+
+    ast_manager& get_manager() { return m; }
+
+};
+
+#endif