reorganizing the code

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

src/ast/substitution/matcher.h

@@ -0,0 +1,64 @@
+/*++
+Copyright (c) 2006 Microsoft Corporation
+
+Module Name:
+
+    matcher.h
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Leonardo de Moura (leonardo) 2008-02-02.
+
+Revision History:
+
+--*/
+#ifndef _MATCHER_H_
+#define _MATCHER_H_
+
+#include"substitution.h"
+#include"hashtable.h"
+
+/**
+   \brief Functor for matching expressions.
+*/
+class matcher {
+    typedef std::pair<expr *, expr *> expr_pair;
+    typedef pair_hash<obj_ptr_hash<expr>, obj_ptr_hash<expr> > expr_pair_hash;
+    typedef hashtable<expr_pair, expr_pair_hash, default_eq<expr_pair> > cache;
+
+    ast_manager &         m_manager;
+    substitution *        m_subst;
+    cache                 m_cache;
+    svector<expr_pair>    m_todo;
+
+    void reset();
+
+public:
+    matcher(ast_manager & m);
+
+    /**
+       \brief Return true if e2 is an instance of e1.
+       In case of success (result is true), it will store the substitution that makes e1 equals to e2 into s.
+       
+       For example:
+       1) e1 = f(g(x), x), e2 = f(g(h(a)), h(a))
+       The result is true, and s will contain x -> h(a)
+
+       2) e1 = f(a, x)     e2 = f(x, a)
+       The result is false.
+
+       3) e1 = f(x, x)     e2 = f(y, a)
+       The result is false
+
+       4) e1 = f(x, y)     e2 = f(h(z), a)
+       The result is true, and s contains x->h(z) and y->a
+    */
+    bool operator()(expr * e1, expr * e2, substitution & s);
+};
+
+#endif /* _MATCHER_H_ */
+