Re: Use of grep with arrays/hashes

I prefer to use the map function for this type of hash population


map {$fields{$_}++} @fields;
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This is not much different than merlyn's; his is probably faster though. I wonder why ...

Comment on Re: Use of grep with arrays/hashes Download Code

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(ar0n) Re (2): Use of grep with arrays/hashes by ar0n (Priest) on May 24, 2001 at 06:49 UTC
his is probably faster though. I wonder why ... Because map takes a list and returns one, whereas for just iterates through one. This idiom is called "map in void context" (not using the list returned by map). It's considered bad form. See What's wrong with using grep or map in a void context?. [ ar0n ]	[reply]
Re (tilly) 2: Use of grep with arrays/hashes by tilly (Archbishop) on May 24, 2001 at 08:05 UTC
Of the two bad idioms, abusing map is worse because if your function returns multiple values per term and you are on any Perl before 5.6.1, the effort of constructing the return list is quadratic. But map and grep work out the same in this case, and the potential difference is largely irrelevant because both run more slowly than simple looping and waste more memory while they are at it. So use a loop.	[reply]