Re: iterating through array and saving matches to new array

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Re^2: iterating through array and saving matches to new array by choroba (Cardinal) on Apr 15, 2018 at 21:46 UTC
`&&` imposes scalar boolean context on the first argument. Therefore, the grep on line 4 iterates over @d only provided @b and @c aren't empty. To iterate over several arrays, use comma: `my @newb = grep $_ > 850, @b, @c, @d;` [download] It's also a good idea to test the code before posting here ;-) ($q=q:Sq=~/;[c](.)(.)/;chr(-\|\|-\|5+lengthSq)`"S\|oS2"`map{chr \|+ord }map{substrSq`S_+\|`\|}3E\|-\|`7**2-3:)=~y+S\|`+$1,++print+eval$q,q,a, [download]	[reply] [d/l] [select]
Re^2: iterating through array and saving matches to new array (updated) by AnomalousMonk (Archbishop) on Apr 15, 2018 at 21:41 UTC
... it works with multiple arrays: ... `my @newb = grep {$_>850}(@b&&@c&&@d);` I'm not sure what you mean by "works" in this context. Is the following output what you expect? `c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le "my @b = (1, 2, 3, 11, 12, 13); my @c = (4, 5, 6, 14, 15, 16); my @d = (7, 8, 9, 17, 18, 19); my @newb = grep { $_ > 10 } (@b && @c && @d); dd \@newb; " [17, 18, 19]` [download] Something seems to have happened to the contents of the `@b` and `@c` arrays. Again, did you intend this? This result comes from the short-circuiting behavior of the `&& \|\| and or` logical operators; see perlop. (Please see the non-core module Data::Dump for the `dd()` function. The core Data::Dumper module has dumper functions that you will not need to install a module to access.) Update: Changed the array initializations in the example code above to make the point more clearly. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^2: iterating through array and saving matches to new array by Marshall (Canon) on Apr 19, 2018 at 19:56 UTC
To make the the "or" of all 3 arrays with unique values > 850, consider this: `#!/usr/bin/perl use strict; use warnings; my @b = 1..1000; my @c = 900..1000; my @d = 910..1000; # my @newb = grep {$_>850}(@b&&@c&&@d); ### will not work! my %seen; my @newb = map{ ($_ > 850 and !$seen{$_}++) ? $_: ()} (@b,@c,@d); print "@newb\n";` [download] I am not sure what the intent here is.	[reply] [d/l]
Re^3: iterating through array and saving matches to new array by AnomalousMonk (Archbishop) on Apr 19, 2018 at 21:32 UTC
Wouldn't the code be more readable/maintainable/etc with List::Util`::uniq()`: `my @newb = uniq grep $_ > 850, @b, @c, @d;` Results are the same per Test::More`::is_deeply()`. (In older Perls, see List::MoreUtils`::uniq`.) Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^4: iterating through array and saving matches to new array by Marshall (Canon) on Apr 19, 2018 at 23:05 UTC
Yes, actually it would be. Although I would still prefer the block form of grep. I show how to use map{} It actually took me quite a while to learn how to return "nothing" instead of "undef" from a map.	[reply]
Re^5: iterating through array and saving matches to new array by AnomalousMonk (Archbishop) on Apr 20, 2018 at 01:29 UTC
Re^6: iterating through array and saving matches to new array by Marshall (Canon) on Apr 20, 2018 at 02:56 UTC
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