Re^2: How to check if a variable's value is equal to a member of a list of values

in reply to Re: How to check if a variable's value is equal to a member of a list of values
in thread How to check if a variable's value is equal to a member of a list of values

Hi,

intersting: Because I'm curious: Is this substantially different (memory footprint, performance) than:

if(grep { $_ eq $string } @array) {
[download]

McA

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Re^3: How to check if a variable's value is equal to a member of a list of values by LanX (Saint) on Mar 25, 2013 at 14:28 UTC
It should smartmatch is implemented in C grep doesn't stop after matching. Unfortunately all the use cases of smartmatch are hard to remember. For repeated lookups a prepared hash scales certainly better. You're free to check this with benchmarks or search for older discussions.š I hoped smartmatch could at least handle the stringification limitation of hashes, but nope: `DB<141> $h1={} => {} DB<142> $h1 ~~ [$h1] => "" DB<143> 5 ~~ [5] => 1` [download] Cheers Rolf ( addicted to the Perl Programming Language) Update š) Brian got deep into benchmarking :) http://stackoverflow.com/questions/3951812/how-fast-is-perls-smart-match-operator-for-searching-scalar-in-an-array	[reply] [d/l]
Re^4: How to check if a variable's value is equal to a member of a list of values by McA (Priest) on Mar 25, 2013 at 14:42 UTC
Thank you. An intersting link. I have to admit that I haven't worked with the smart match operator. It's a little bit too much "Eierlegendenwollmilchsau" (1) for me. And what I read about it confirmed to wait with it. But probably I'm too old fashioned. McA (1) Best translation I could find on dict.leo.org: jack of all trades device	[reply]
Re^3: How to check if a variable's value is equal to a member of a list of values by dbuckhal (Chaplain) on Mar 26, 2013 at 21:29 UTC
Just to toss in a tidbit, and not trying to hijack the thread, but while benchmarking an alternative to using the smart match operator, I discovered that using map in scalar content performed better than grep. `if( map { /$string/ } @array) {` [download] rather than... `if( grep { /$string/ } @array) {` [download] I was surprised, because either way you'd be getting a non-undef value to satisfy the conditional, but map did it faster. I can post my code in a new thread if anyone's interested, otherwise, carry on! :)	[reply] [d/l] [select]
Re^4: How to check if a variable's value is equal to a member of a list of values by LanX (Saint) on Mar 26, 2013 at 21:37 UTC
`grep { TEST } LIST` is semantically equivalent to `map { TEST ? $_ : () } LIST` Seems obvious that more logic results in longer runtime. Don't you think so? Cheers Rolf ( addicted to the Perl Programming Language)	[reply] [d/l] [select]
Re^5: How to check if a variable's value is equal to a member of a list of values by dbuckhal (Chaplain) on Mar 26, 2013 at 22:55 UTC
Yes, I would agree that more logic increases runtime, but from your example, are you saying that `grep` should be faster? Please explain your example, so I understand you clearly. Personally, I have no idea how `grep`, `map`, or `~~` all work "under the hood". In your syntax, I see `grep` and `map` both iterating over the list, so my guess was they would have performed equally. I was surprised at my results.	[reply] [d/l] [select]
Re^6: How to check if a variable's value is equal to a member of a list of values by LanX (Saint) on Mar 26, 2013 at 23:00 UTC

In Section Seekers of Perl Wisdom

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