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in reply to Re: Shift versus Sanity
in thread Shift versus Sanity

sorry juerd, can't agree. another common idiom that noone's mentioned is this:

sub do_stuff { my $this = shift; my $session = shift || die "Missing req'd Session argument"; my $cgi = shift || new CGI (); ... }

aesthetics aside, here are some hard figures on efficiency (slightly reformatted):

[matt@dirty matt]$ ./test_arg_passing.pl Benchmark: timing 2000000 iterations of argumentative_1arg, argumentative_3args, direct_1arg, direct_3args, shifty_1arg, shifty_3args... argumentative_1arg: 17 wallclock secs (17.69 usr + 0.01 sys = 17.70 CPU) @ 112994.35/s (n=2000000) argumentative_3args: 21 wallclock secs (21.93 usr + 0.02 sys = 21.95 CPU) @ 91116.17/s (n=2000000) direct_1arg: 10 wallclock secs (10.86 usr + 0.04 sys = 10.90 CPU) @ 183486.24/s (n=2000000) direct_3args: 13 wallclock secs (12.24 usr + 0.02 sys = 12.26 CPU) @ 163132.14/s (n=2000000) shifty_1arg: 17 wallclock secs (18.07 usr + 0.03 sys = 18.10 CPU) @ 110497.24/s (n=2000000) shifty_3args: 23 wallclock secs (23.91 usr + 0.01 sys = 23.92 CPU) @ 83612.04/s (n=2000000) total: 42000000

not much of a difference, though the triple shift example is a bit pathological. here's the code for the above:

#!/usr/bin/perl -w use Benchmark; use strict; package ArgTest; sub shifty_1arg { my $this = shift; my $first_arg = shift; $$this += $first_arg; } sub shifty_3args { my $this = shift; my $first_arg = shift; my $second_arg = shift; my $third_arg = shift; $$this += $first_arg + $second_arg + $third_arg; } sub argumentative_1arg { my( $this, $first_arg ) = @_; $$this += $first_arg; } sub argumentative_3args { my( $this, $first_arg, $second_arg, $third_arg ) = @_; $$this += $first_arg + $second_arg + $third_arg; } sub direct_1arg { ${$_[0]} += $_[1]; } sub direct_3args { ${$_[0]} += $_[1] + $_[2] + $_[3]; } sub value { return ${$_[0]} } package main; my $total; bless( my $object = \$total, 'ArgTest' ); my @args = ( 1 .. 3 ); timethese( 2_000_000, { shifty_1arg => sub { $object->shifty_1arg( @args ) }, argumentative_1arg => sub { $object->argumentative_1arg( @args ) }, direct_1arg => sub { $object->direct_1arg( @args ) }, shifty_3args => sub { $object->shifty_3args( @args ) }, argumentative_3args => sub { $object->argumentative_3args( @args ) }, direct_3args => sub { $object->direct_3args( @args ) }, } ); print "total: " . $object->value . "\n";

matt