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

by tobyink (Abbot)
on Dec 07, 2012 at 16:51 UTC ( #1007791=note: print w/ replies, xml ) Need Help??


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


Comment on Re: new keyword "size" to avoid scalar trap ? ( scalar @array != scalar(LIST) )
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Re^2: new keyword "size" to avoid scalar trap ? ( scalar @array != scalar(LIST) )
by LanX (Canon) on Dec 07, 2012 at 17:04 UTC
    hmm good point...

    you are forcing everything into an array,

    maybe

    sub size { scalar @_ }
    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

      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);

      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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