If /Else Structure when If is used in latter part of a line.

jerrygarciuh has asked for the wisdom of the Perl Monks concerning the following question:

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Re: If /Else Structure when If is used in latter part of a line. by lestrrat (Deacon) on Sep 30, 2001 at 21:00 UTC
You can't. Just use the normal expression : `foreach (@input) { if( exists $list{ $_ } ) { push @name_nums, $list{$_}; } else { push @name_names, $_; } }` [download] TMTOWTDI : `foreach my $input (@input ) { push @name_nums, ( exists $list{ $input } ? $list{ $input } : $in +put ); } ## following will not work if $list{ $input } can be 0 or undef, ## but here's another way foreach my $input ( @input ) { push @name_nums, ( $list{ $input } \|\| $input ); }` [download]	[reply] [d/l] [select]
Re: If /Else Structure when If is used in latter part of a line. by demerphq (Chancellor) on Sep 30, 2001 at 21:33 UTC
Hi Jerry The simple answer is, you cant. A better answer is that an if statement used as you have done is not a compund if statement, but an if statement modifier (see perlsyn). Consider `my $x=1 if $y; # statement modifier if ($y) {my $x=1} # compund statement` [download] The two are very different. The first declares $x to be in scope and if $y is true initializes it to 1. The second checks to see if $y is true, then declares $x to be equal to 1 _within_ its own scope, so $x wont be available after the if completes. But it seems to me that what you want is one of the two following snippets. `# first variant, dont do this. foreach (@input){ push @name_nums, (exists $list{$_}) ? $list{ $_ } : $_; } # second variant, do this @name_nums=map{(exists $list{$_}) ? $list{ $_ } : $_}@input;` [download] This is precisely the task that map was invented for. Basically apply a function to every element of an array putting the results in another array. `Update` The solutions above use the secret third kind of if. Its called the Conditional Operator or sometime the ternary operator and works like this: condition ? result : other result Where result and other result are evaluated for the value they return. This can very useful when you need an if in a place where normally an if is prohibitied. You may need to add parenthesis depending on the situation. An example is below: `print "Hello my name is ".(defined $name ? $name : "Anonymous Monk")." +\n";` [download] HTH Yves -- You are not ready to use symrefs unless you already know why they are bad. -- tadmc (CLPM)	[reply] [d/l] [select]