in reply to Re^4: Hash sorting (by value) woes
in thread Hash sorting (by value) woes

True, but it would be slower.

print map { ...1... } ...2...;

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is closer to

@temp_list = map { ...1... } ...2...;
print @temp_list;

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than to

print ...1... foreach ...2...;

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The extra assignment slows things down. (About twice as slow, IIRC previous tests.)

Update: Fixed brain fart R.J. noticed.

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Re^6: Hash sorting (by value) woes
by Roy Johnson (Monsignor) on Feb 24, 2005 at 18:03 UTC
    Isn't it more like 
    @temp_list = map { ...1... } ...2....;
print @temp_list;

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    ? The map is done before print sees it, and print is only called once, with a list. It is slower, of course, because you do have an extra list-building step. Interestingly, it is not slower than map in a void context (I'm using 5.8.0 here -- when was that optimized?): 
    use Benchmark 'cmpthese';
my @vals = (10_000..15_000);

open(ABYSS, '>', '/dev/null') or die "The abyss is closed.\n";

cmpthese(-2, {
    'map' => sub { print ABYSS map {">>$_<<\n"} @vals },
    'map_void' => sub { map {print ABYSS ">>$_<<\n"} @vals },
    'for' => sub { print ABYSS ">>$_<<\n" for @vals }
});

close ABYSS;
__END__
           Rate map_void      map      for
map_void 11.9/s       --     -23%     -50%
map      15.5/s      30%       --     -34%
for      23.6/s      99%      52%       --

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    Caution: Contents may have been coded under pressure.
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