> -----Original Message----- > From: Chris Charley [mailto:[EMAIL PROTECTED] > Sent: Friday, February 04, 2005 10:45 AM > To: beginners@perl.org > Subject: Re: Variable-sized hash of booleans > > > > You can use grep. > > > > my %hash = (ONE => 1, TWO => 0, THREE => 1); > > > > if (grep {! $hash{$_}} keys %hash) { > > print "false\n"; > > } > > else { > > print "true\n"; > > } > > > > Prints 'false'. > > Guess it would be helpful to explain how grep works here. > From the perlfunc > man page: > Evaluates the BLOCK or EXPR for each element of LIST (locally > setting $_ to > each element) and returns the list value consisting of those > elements for > which the expression evaluated to true. In scalar context, > returns the > number of times the expression was true. > > In the code above, ! $hash{$_} evals to true when $hash{TWO} > is evaluated, > so grep, being in scalar context, would return 1, the number > of elements in > %hash which evaluated to 'true '.If all values were 'true', > (1's), then grep > would return 0 since !$hash{$_} would be false for every > element in that > case. > > Chris >
Oh! I got my true/false 's backwards cause of the '!' in there. Thanks for the explanation Chris. --Errin -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] <http://learn.perl.org/> <http://learn.perl.org/first-response>
