Added stub for DATEDIFF function.

Operand.cpp

@@ -364,7 +364,21 @@ namespace jet {
 	    int unixtime = seconds_since_epoch.count();	    
 	    string << unixtime;
 	 } else
-	   throw coreutils::Exception("Expecting ) at end of UNIXTIME.");	 	 	 	 	 	 
+	   throw coreutils::Exception("Expecting ) at end of UNIXTIME.");
+      }
+      else if(in.ifNextIgnoreCase("DATEDIFF")) {
+	 if(!in.ifNext("("))
+	   throw coreutils::Exception("Expecting ( for DATEDIFF.");
+	 Operand parm1(in, tag);
+	 if(!in.ifNext(","))
+	   throw coreutils::Exception("Expecting , in DATEDIFF expression.");
+	 Operand parm2(in, tag);
+	 if(in.ifNext(")")) {
+
+	    // TODO: Implement DATEDIFF.
+
+	 } else
+	   throw coreutils::Exception("Expecting ) at end of DATEDIFF expression.");	 	       
       } else if(in.ifNextIgnoreCase("true")) {
 	 boolean = true;
 	 string = "true";