* src/ltlvisit/equals.cc, src/ltlvisit/equals.hh: New files.

* src/ltlvisit/Makefile.am (libltlvisit_a_SOURCES): Add equals.hh
and equals.cc.
* src/ltltest/equals.cc, src/ltltest/equals.test: New files.
* src/ltltest/Makefile.am (check_PROGRAMS): Add equals.
(equals_SOURCES): New variable.
(TESTS): Add equals.test.

src/ltlvisit/equals.hh

@@ -0,0 +1,34 @@
+#include "ltlast/formulae.hh"
+#include "ltlast/visitor.hh"
+
+namespace spot 
+{
+  namespace ltl
+  {
+    // This visitor is public, because it's convenient
+    // to derive from it and override part of its methods.
+    class equals_visitor : public const_visitor
+    {
+    public:
+      equals_visitor(const formulae* f);
+      virtual ~equals_visitor();
+
+      // Return true iff the visitor has visited a
+      // formulae which is equal to `f'.
+      bool result() const;
+      
+      void visit(const atomic_prop* ap);
+      void visit(const unop* uo);
+      void visit(const binop* bo);
+      void visit(const multop* bo);
+      void visit(const constant* c);
+	
+    private:
+      const formulae* f_;
+      bool result_;
+	      
+    };
+
+    bool equals(const formulae* f1, const formulae* f2);
+  }
+}