Z3 sources

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

lib/occurs.cpp

@@ -0,0 +1,77 @@
+/*++
+Copyright (c) 2006 Microsoft Corporation
+
+Module Name:
+
+    occurs.cpp
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Leonardo de Moura (leonardo) 2007-06-07.
+
+Revision History:
+
+--*/
+#include"occurs.h"
+
+#include"for_each_expr.h"
+
+// -----------------------------------
+//
+// Occurs check
+//
+// -----------------------------------
+
+namespace occurs_namespace {
+    struct found {}; 
+    
+    struct proc {
+        expr * m_n;
+
+#define CHECK() { if (n == m_n) throw found(); }
+
+        proc(expr * n):m_n(n) {}
+        void operator()(var const * n) { CHECK(); }
+        void operator()(app const * n) { CHECK(); }
+        void operator()(quantifier const * n) { CHECK(); }
+    };
+
+    struct decl_proc {
+        func_decl * m_d;
+
+        decl_proc(func_decl * d):m_d(d) {}
+        void operator()(var const * n) { }
+        void operator()(app const * n) { if (n->get_decl() == m_d) throw found(); }
+        void operator()(quantifier const * n) { }
+    };
+
+
+};
+
+// Return true if n1 occurs in n2
+bool occurs(expr * n1, expr * n2) {
+    occurs_namespace::proc p(n1);
+    try {
+        quick_for_each_expr(p, n2);
+    }
+    catch (occurs_namespace::found) {
+        return true;
+    }
+    return false;
+}
+
+bool occurs(func_decl * d, expr * n) {
+    occurs_namespace::decl_proc p(d);
+    try {
+        quick_for_each_expr(p, n);
+    }
+    catch (occurs_namespace::found) {
+        return true;
+    }
+    return false;
+}
+