>> Which language(s) do you know that has such a feature? > > I should came from Marco Cantu's Delphi 2005 book, that I have read just > recently. > But I am unable to find it again.
I'd be very surprised if it came from Delphi for two reasons: a) I used Delphi a lot for several years and never came across it! :-) b) Delphi (or Object Pascal) is strictly statically typed and wouldn't even compile with any undefined values in the code. BUT... I just checked and it *is* in Delphi - a new feature in Delphi 6. BUT it's not a language feature rather it is a compiler directive like the C #ifdef. (And starts with uppercase D BTW). His example: //-------------------- const debugControl = 2 {$IF Defined(DEBUG) and DebugControl > 3} // do stuff here {$IFEND} //--------------------- There is also a Declared directive too. These are not primarily intended for determining whether a variable is defined or declared but to determine whether a particular language feature has been defined or constant declared in the current version of Delphi (post version 6 of course!) Now that's an entirely different question in terms of how we do that in Python! Which I'll lreave as an excercise for the readers ;-) -- Alan G Author of the learn to program web tutor http://www.freenetpages.co.uk/hp/alan.gauld _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor