reorganizing the code

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

src/ast/rewriter/dl_rewriter.cpp

@@ -0,0 +1,57 @@
+/*++
+Copyright (c) 2010 Microsoft Corporation
+
+Module Name:
+
+    dl_rewriter.cpp
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2010-08-10
+
+Revision History:
+
+--*/
+
+#include"dl_rewriter.h"
+    
+    br_status dl_rewriter::mk_app_core(
+        func_decl * f, unsigned num_args, expr* const* args, expr_ref& result) {
+        ast_manager& m = result.get_manager();
+        uint64 v1, v2;
+        switch(f->get_decl_kind()) {
+		case datalog::OP_DL_LT:
+            if (m_util.is_numeral_ext(args[0], v1) &&
+                m_util.is_numeral_ext(args[1], v2)) {
+                result = (v1 < v2)?m.mk_true():m.mk_false();
+                return BR_DONE;
+            }
+            // x < x <=> false
+            if (args[0] == args[1]) {
+                result = m.mk_false();
+                return BR_DONE;
+            }
+            // x < 0 <=> false
+            if (m_util.is_numeral_ext(args[1], v2) && v2 == 0) {
+                result = m.mk_false();
+                return BR_DONE;
+            }
+            // 0 < x <=> 0 != x
+            if (m_util.is_numeral_ext(args[1], v1) && v1 == 0) {
+                result = m.mk_not(m.mk_eq(args[0], args[1]));
+                return BR_DONE;
+            }
+            break;
+
+        default:
+            break;
+        }
+        return BR_FAILED;
+    }
+    
+
+