Re: reduce like iterators

[LanX]

Hello younger me :)

> and List::MoreUtils doesn't seem to provide anything better

This changed in the meantime, slide was added, but there are still issues.

The worst one is that it only returns scalars instead of lists like map does, which means we have to add an extra grep to filter undefined values :/

use v5.12;
use warnings;
use List::MoreUtils qw/slide/; 
use Data::Dump;


my @x= split',', q(a,a,a,a,b,c,c,a,a,d,e,e,e,e);

dd grep defined, slide { $a ne $b ? $b : () } "", @x;

[LanX]

> The worst one is that it only returns scalars instead of lists like map does, which means we have to add an extra grep to filter undefined values :/

That's most likely a bug in the XS implementation of slide.

I looked into the Pure Perl implementation in List::MoreUtils::PP, and it looked fine, it's literally using map

And a test reveals, that it really works like it should.

use v5.12;
use warnings;
use Data::Dumper;
BEGIN { $ENV{LIST_MOREUTILS_PP} = 1 }; # enforce PP version, comment f
+or XS
use List::MoreUtils qw/slide/;

my @x= split',', q(a,a,a,a,b,c,c,a,a,d,e,e,e,e);

print Dumper slide { $a ne $b ? $b : () } "", @x;

PP version

$VAR1 = 'a';
$VAR2 = 'b';
$VAR3 = 'c';
$VAR4 = 'a';
$VAR5 = 'd';
$VAR6 = 'e';

XS version

$VAR1 = 'a';
$VAR2 = undef;
$VAR3 = undef;
$VAR4 = undef;
$VAR5 = 'b';
$VAR6 = 'c';
$VAR7 = undef;
$VAR8 = 'a';
$VAR9 = undef;
$VAR10 = 'd';
$VAR11 = 'e';
$VAR12 = undef;
$VAR13 = undef;
$VAR14 = undef;

[choroba]

> That's most likely a bug in the XS implementation of slide.

The word "bug" should be a link to the actual bug report.

[LanX]

I already reported it in private, it's complicated....