in reply to truth in while condition

Truthiness is also discussed in Truth and Falsehood in perlsyn. As has been pointed out by others, you were testing "0\n" in the while-loop conditional and not the truly false string "0".

Update: At last, I see the point first made by LanX here: even if  <STDIN> managed to return a plain, nominally false  "0" character, the loop would still execute because  "0" is defined and the special-case while-loop is conditional upon defined-ness! Thanks to BillKSmith (here) and LanX (here) for helping the scales to fall from my eyes.

Give a man a fish:  <%-{-{-{-<

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Re^2: truth in while condition
by LanX (Saint) on Sep 30, 2018 at 21:55 UTC
    > you were testing "0\n" in the while-loop conditional and not the truly false string "0".

    The following iterator returns no "\n" but still fails to stop at "truly false" number 0.

    see explanation here

     
use strict;
use warnings;
use feature 'say';


my $i = Iterator->new([1,0,2,undef,3]);

while ( <$i> ) {
    say "<$_>";
}


package Iterator;

use overload
  '<>' => sub {
      shift @{$_[0]}
  };

sub new {
    my ($class,$obj) =@_;
    bless $obj, $class;
}

    [download]

    -->

    <1>
<0>
<2>

    [download]

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery FootballPerl is like chess, only without the dice

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Re^2: truth in while condition
by BillKSmith (Monsignor) on Sep 30, 2018 at 21:25 UTC
    The reference in the first reply LanX explains that in this case, 'while' tests 'definedness' not 'Truthiness'.
    Bill
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