in reply to Interesting Use for "state" Variables

The D language has a nice pragmatic variation on the foreach loop.

Written this way, c takes on each of the values in the array a in turn: 

char[] a;
...
foreach (char c; a) {
...
}

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Written this way, the same thing happens, but also i takes on the index of the value also: 

char[] a;
...
foreach (int i, char c; a)

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I don't think there's any possibility of getting that into 5.12 (nor even Perl 6 at this late stage), but it one of those few features of other languages I miss when I'm writing Perl.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

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Re^2: Interesting Use for "state" Variables
by massa (Hermit) on Mar 10, 2009 at 02:53 UTC
    perl6 already has the kv thingy:
    for @x.kv -> $index, $value {
  say $index, ' ', $value
}

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    (tested with rakudo, it works)
    []s, HTH, Massa (κς,πμ,πλ)
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Re^2: Interesting Use for "state" Variables
by eyepopslikeamosquito (Archbishop) on Mar 10, 2009 at 15:44 UTC

    Python has enumerate for this. For example: 

    for i, item in enumerate(array):
    do_something_with(item, i)

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    The nearest thing I can find to that in Perl is the List::MoreUtils pairwise function, something like: 
    my @idx = 0 .. $#array;
pairwise { do_something_with($b, $a) } @idx, @array;

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    or perhaps the CPAN Array::Each::Override module.

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      You can achieve something similar without modules a couple of ways: 

      @a = 'A'..'J'; 
for my $r ( map { k=> $_, v=> $a[ $_ ] }, 0 .. $#a ) { 
    print "@{ $r }{ k, v }\n" 
}

0 A
1 B
2 C
3 D
4 E
5 F
6 G
7 H
8 I
9 J

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      Or

      @a = 'A'..'J'; 
for my $r ( map [ $_, $a[ $_ ] ], 0 .. $#a ) { 
    print "$r->[0]:$r->[1]\n" 
}
0:A
1:B
2:C
3:D
4:E
5:F
6:G
7:H
8:I
9:J

      [download]
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
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In Section Meditations