Jeff Westman wrote: > Hi, > > In my limited experience with perl, I've never had to use the 'amp' command, > even though I see it used all the time. It seems to just be a short-cut of > other commands/keywords that I've used. > > So, when do you HAVE to use 'map', when no other option makes sense?! >
When you want to preserve an array, but generate a second one based on some function of each element. Greetings! E:\d_drive\ocf\discuss\prototype>perl -w my @source = (3, 6, 7, 9); my @target = map $_ + 1, @source; print "$_ " for @source; print "\n"; print "$_ " for @target; print "\n"; ^Z 3 6 7 9 4 7 8 10 It should ot be used to modify the elements in the original. You are right--that is what a for() loop is for. You should be careful to avoid processes that affect the default variable, because they can have evil side-effects: Greetings! E:\d_drive\ocf\discuss\prototype>perl -w my @source = (3, 6, 7, 9); my @target = map ++$_, @source; print "$_ " for @source; print "\n"; print "$_ " for @target; print "\n"; ^Z 4 7 8 10 4 7 8 10 ...or worse. That was actually my second try at illustrating the problem. The first, using the more familiar postfix increment, had even more horrid results: Greetings! E:\d_drive\ocf\discuss\prototype>perl -w my @source = (3, 6, 7, 9); my @target = map $_++, @source; print "$_ " for @source; print "\n"; print "$_ " for @target; print "\n"; ^Z 4 7 8 10 3 6 7 9 ... as in, the completely wrong array got changed. Tthere are many good uses for mappings, I can assure you. They just should not be used for their side effects Joseph -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
