in reply to new keyword "size" to avoid scalar trap ? ( scalar @array != scalar(LIST) )

Do you even need prototypes?

use 5.010;

sub size { @_ + 0 }

say size 'a' .. 'z';

my @foo = (1, 2, 3);
say size @foo;

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perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
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Re^2: new keyword "size" to avoid scalar trap ? ( scalar @array != scalar(LIST) )
by LanX (Saint) on Dec 07, 2012 at 17:04 UTC
    hmm good point...

    you are forcing everything into an array,

    maybe 

    sub size { 
  scalar @_ 
}

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    is easier to read.

    it's like explicitly wrapping lists and arrays into scalar @{[ ... ]}

    But w/o prototypes this would mean to copy huge arrays around...

    And something like size %hash couldn't be extended to find scalar keys %hash.

    Anyway your example fits as a proof of concept! =)

    (But an efficient implementation should be done in XS. Edit: see benchmark)

    Cheers Rolf

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      Inline::C allows a pretty fast implementation...

      use 5.010;
use Benchmark qw(cmpthese);
use Inline C => <<'INLINE';
int count1 (SV* name1, ...)
{
   Inline_Stack_Vars;
   return Inline_Stack_Items;
}
INLINE

sub count2 { scalar @_ }
sub count3 { 0 + @_ }
sub count4 { my $_ = @_ }
sub count5 (\@) { scalar @{$_[0]} }

my @array = 'a'..'z';

my %implementations = (
    count1 => sub { count1(@array) },
    count2 => sub { count2(@array) },
    count3 => sub { count3(@array) },
    count4 => sub { count4(@array) },
    count5 => sub { count5(@array) },
);

for my $i (sort keys %implementations) {
    say $i, ": ", $implementations{$i}->();
}

cmpthese(250_000, \%implementations);

      [download]

      XS may well allow faster still.

      perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
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