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Re^2: How to call a function on each item after a split?

by Lotus1 (Chaplain)
on Oct 10, 2012 at 02:40 UTC ( #998117=note: print w/ replies, xml ) Need Help??


in reply to Re: How to call a function on each item after a split?
in thread How to call a function on each item after a split?

Your demonstration of using grep like that only works if the function modifies $_. Your example makes it seem that map and grep are equivalent which they aren't. grep looks at the return value in the block to determine whether or not to pass along $_ while map passes along the return value in the block. Big difference. If one of the values in the string happens to be '0' then grep doesn't pass that value through. Also your solution doesn't pass along the final empty string like the one with the map{ clean($_);$_ } solution did.

#!/usr/bin/perl use strict; use warnings; my $str = "item1 | 0 | | item2| item3 |item4 | "; my @cleaned1 = map { clean_no_side_effects($_) } split( /\|/, $str ); my @cleaned2 = grep { clean_no_side_effects($_) } split( /\|/, $str ); print "*"x25, "\n"; print join "\n", @cleaned1; print "*"x25, "\n"; print join "\n", @cleaned2; print "*"x25, "\n"; sub clean_no_side_effects { my $string = shift; $string =~ s/^\s+|\s+$//g; return $string; } sub clean_modify { ## don't use, still using side effects for grep t +o work $_[0] =~ s/^\s+?|\s+?$//g; # '?' isn't needed here since \s neve +r matches '|' return $_[0]; } sub clean { ## don't use chomp( $_[0] ); $_[0] =~ s/^\s+//g; $_[0] =~ s/\s+$//g; } __END__ ************************* item1 0 item2 item3 item4 ************************* item1 item2 item3 item4 *************************


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