Re^2: Fence vs. Posts

I like your suggestion of the 'for modifier'. Note however, that it requires the 'push' function to do the same thing as map.

C:\Users\Bill\forums\monks>type rodinski.pl
use strict;
use warnings;
use Data::Dumper;

my @arry = qw(A B C);

my @gaps;
push @gaps, [$arry[$_], $arry[$_+1]] for 0..$#arry-1;


print Dumper(\@gaps);

C:\Users\Bill\forums\monks>perl rodinski.pl
$VAR1 = [
          [
            'A',
            'B'
          ],
          [
            'B',
            'C'
          ]
        ];
[download]

Bill

Comment on Re^2: Fence vs. Posts Download Code

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Re^3: Fence vs. Posts by haukex (Archbishop) on Jun 10, 2018 at 09:55 UTC
Sorry, I realize now that putting those two sentences next to each other probably made my post a bit confusing. When I said "using `map` purely for its side-effects", I was referring to these lines in the OP's code: `map { printf "%15s to %-15s\n", $_->[0],$_->[1] } pairs @legs; map { if ($info{$_->[0]}{state} ne $info{$_->[1]}{state}) {say "Mann +Act!"} } pairs @legs; map { $info{$_[0]}{"state"}=$_[1] } pairs mesh @trip, @states;` [download] The return value of `map` is completely ignored, and instead actions are taken inside the code block that have side effects. These are the cases where I think a `for` statement modifier would be better. On the other hand, the code that I showed, `map {@arr[$_,$_+1]} 0..$#arr-1` does not make any modifications to the `@arr`, and I do use the return value - so this is a case where I would perfer `map` over `for`.	[reply] [d/l] [select]

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Re^3: Fence vs. Posts
by haukex (Archbishop) on Jun 10, 2018 at 09:55 UTC

Sorry, I realize now that putting those two sentences next to each other probably made my post a bit confusing. When I said "using map purely for its side-effects", I was referring to these lines in the OP's code:

map { printf "%15s to %-15s\n", $_->[0],$_->[1] } pairs @legs; map { if ($info{$_->[0]}{state} ne $info{$_->[1]}{state}) {say "Mann +Act!"} } pairs @legs; map { $info{$_[0]}{"state"}=$_[1] } pairs mesh @trip, @states;
[download]

The return value of map is completely ignored, and instead actions are taken inside the code block that have side effects. These are the cases where I think a for statement modifier would be better.

On the other hand, the code that I showed, map {@arr[$_,$_+1]} 0..$#arr-1 does not make any modifications to the @arr, and I do use the return value - so this is a case where I would perfer map over for.

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