>if (defined $x and length $x) > >So, is this the opposite? > >if (! defined $x and ! length $x)
I don't think so. It's basic Aristotelian logic and can be determined by truth tables or testing. Questions are mere conjecture :) The negative of a statement, A, is: not A. That can be writted as: ! A (with a difference in precedence binding. See http://www.perldoc.com/perl5.6/pod/perlop.html) Now, A may be a conjunctive statement, such as ( B and C ). That means the negative would be: 1. not ( B and C ) or 2. ! (B and C) By truth tables or experimentation that be be proved equivilant to the following disjunctive statement: 3. ( (! B) or (!C) ) or 4. ( (not B) or (not C) ) It is not equivilant to 5. ( (! A) and (!B) ) or 6. ( ! (A and (!B) ) Because (B and C) is true only if (B is true and C is true), and it is false if either (B is false xor C is false) or (both B and C are false). If you use parenthesis as in statements (3) and (4) above, then you do not need to worry about operator binding rules. If you want to craft very compact statements and programs to win perl golf tournaments, that is the time to rely on the operator associativity and precedence rules to eliminate all the parentheses you can! (((((unless the game is to confound your opponent with a lot of parentheses))))) If you get really good at using a plethora of parentheses in even small programs, then maybe you will like Lisp - (car '(a (b (c (d (e (f (g (h (i (j (l (m n) o) p) q) r) s) t) u) v) w) y) z)) => a (http://www.lns.cornell.edu/public/COMP/info/emacs-lisp-intro/emacs-lisp -intro_8.html) -tristram -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
