in reply to printing hashes

Because hashes don't interpolate into quotes. Which is kind of like saying "Because."

No sensible, generally useful hash-to-string conversion was proposed. So there isn't one. Without quotes, it gets turned into a list, and each element is printed.

Caution: Contents may have been coded under pressure.

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Re^2: printing hashes
by TimToady (Parson) on May 07, 2005 at 01:39 UTC
    Perl 6 will interpolate spacetab-separated pairs, one per line, though the restrictions on interpolating arrays and hashes are tightened a bit to avoid accidental interpolation of email addresses and printf formats. You have to do something like: 
        say "Array is @array[]";
    say "Array is {@array}";
    say "Hash is %hash{}";
    say "Hash is {%hash}";

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    Only scalars interpolate without some kind of bracketing.

    The space-separated form was chosen to make it easy to split on whitespace, but it's expected that most hash interpolations will in fact specify some more explicit format: 

        say "Hash is %hash.as('%s => %s', ', ')";

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      Looks like pugs does most of this: 

      $ pugs -e'my @array=1..5;say "Array is @array[]";'
Array is 1 2 3 4 5
$ pugs -e'my @array=1..5;say "Array is {@array}";'
Array is 1 2 3 4 5
$ pugs -e'my %hash;%hash{"a".."c"}=1..3;say "Hash is %hash{}"'
Hash is a    1
b    2
c    3

$ pugs -e'my %hash;%hash{"a".."c"}=1..3;say "Hash is {%hash}"'
Hash is a    1
b    2
c    3

$ pugs -e'my %hash;%hash{"a".."c"}=1..3;say "Hash is %hash.as(q(%s => 
+%s), q(, ))";'
*** Error: No compatible subroutine found: "&as" at -e line 1, column 
+35-73
$

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      Pugs version is 6.2.2.

      After Compline,
      Zaxo

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Re^2: printing hashes
by tlm (Prior) on May 06, 2005 at 02:19 UTC

    I'm surprised you didn't propose this variant of your earlier post today: 

    use List::Util 'reduce';

my %hash = ( foo => 1, bar => 2, baz => 3 );
my $count = 0;
print +( reduce {$a . (++$count % 2 ? ' => ' : ', ') . $b}
         %hash ), $/;
__END__
bar => 2, baz => 3, foo => 1

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    ...or any other of the other join alternation schemes.

    the lowliest monk

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      In that case, the question was "How do I get the output format I want?" This is a case of "Why doesn't Perl interpolate hashes in strings?" I only shamelessly plug my previous posts when it's justified.

      Of course, with the right syntax, Perl will interpolate anything in a string. 

      my %hash = ( foo => 1, bar => 2, baz => 3 );
print "@{[%hash]}";

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      But here's another reducing scheme that doesn't involve strenuous exercise or counting calories: 
      print((reduce { $a . ($$...$$ ? ' => ' : ',') . $b } %hash), $/);

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       The flip-flop doesn't maintain state between calls because in this case, it's not the same flip-flop on each call! Each entry into a subroutine gets a "different" flip-flop.
      Caution: Contents may have been coded under pressure.
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