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Re: Why does the first $c evaluate to the incremented value in [$c, $c += $_] ?

by hazylife (Monk)
on Mar 04, 2014 at 20:58 UTC ( [id://1076957]=note: print w/replies, xml ) Need Help??


in reply to Why does the first $c evaluate to the incremented value in [$c, $c += $_] ?

Very strange indeed. And it doesn't even have to be a state variable, i.e.

my $c = 0;
my @partitions = map { [$c, $c += $_] } @widths;

[download]

gives the same result.

Whereas [$c+0, $c += $_] produces

[0, 2]
[2, 8]
[8, 13]
[13, 20]

[download]
and so does [my $tmp = $c, $c += $_]

Replies are listed 'Best First'.
Re^2: Why does the first $c evaluate to the incremented value in [$c, $c += $_] ?
by derby (Abbot) on Mar 04, 2014 at 21:23 UTC

    Wild guess here but since the anonymous array is on the right side of a list operator, then the comma has really low precedence -- lower than assignment. By adding the +0, you give both terms equal precedence so it goes back to leftward precedence? Well ... that's my guess.

    -derby

    update: what Eily says makes better sense given the simple example of 

    use Data::Dumper;

my $c = 0;
my $d = [ $c, $c += 2 ];

print Dumper( $d );

    [download]

[reply]
[d/l]

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