Beefy Boxes and Bandwidth Generously Provided by pair Networks
Welcome to the Monastery
 
PerlMonks  

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) )
Download Code
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'

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1007791]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others surveying the Monastery: (6)
As of 2015-07-03 00:04 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (47 votes), past polls