Is List::MoreUtils::none buggy?
I think none
subroutine from List::MoreUtils
does not act as described. According to documentation,
none BLOCK LIST Logically the negation of any. Returns a true value if no item in LIST meets the criterion given through BLOCK, or if LIST is empty. Sets $_ for each item in LIST in turn
Now, try:
use strict;
use warning开发者_JAVA技巧s;
use 5.012;
use List::MoreUtils qw(none);
my @arr = ( 1, 2, 3 );
if ( none { $_ == 5 } @arr ) {
say "none of the elements in arr equals 5";
}
else {
say "some element in arr equals 5";
}
works OK, but replace @arr
with an empty one (my @arr = ();
or simply my @arr;
) and you get a wrong answer.
What's going on?
update: i had List::MoreUtils ver 0.22. Updated to the latest and it seems OK. Weird though!
The documentation is in line with the v 0.33 pure Perl implementation. The reason why it failed was because the implementation changed between versions 0.22 and 0.33.
In v 0.33, if @array
is empty, the for
loop will not execute, so YES
will be returned.
Here are the two versions side-by-side:
# v 0.33 | # v 0.22
------------------------------+----------------------------------------
sub none (&@) { | sub none (&@) {
my $f = shift; | my $f = shift;
foreach ( @_ ) { | return if ! @_; # root cause
return NO if $f->(); | for (@_) {
} | return 0 if $f->();
return YES; | }
} | return 1;
| }
MetaCPAN
also provides a comprehensive diff between versions 0.22 and 0.33
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