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Re^4: counting backward

by BrowserUk (Pope)
on Mar 04, 2013 at 03:28 UTC ( #1021568=note: print w/ replies, xml ) Need Help??


in reply to Re^3: counting backward
in thread counting backward

There are still plenty more ways to skin that cat :)

Why subtract and add; when you can just subtract. And why compare to zero when it is unnecessary:

#! perl use strict; use warnings; use Benchmark qw( cmpthese ); my $n = 1e6; my $foreach_loop_total = 0; my $c_for_loop_total = 0; my $while_loop_total = 0; my $while_loop_total2 = 0; cmpthese 100, { foreach_loop => \&foreach_loop, c_for_loop => \&c_for_loop, while_loop => \&while_loop, while_loop2 => \&while_loop2, }; print "\$foreach_loop_total = $foreach_loop_total\n"; print "\$c_for_loop_total = $c_for_loop_total\n"; print "\$while_loop_total = $while_loop_total\n"; print "\$while_loop_total2 = $while_loop_total2\n"; sub foreach_loop { $foreach_loop_total -= $_ for -$n .. 0; } sub c_for_loop { for (my $j = $n; $j >= 0; --$j) { $c_for_loop_total += $j; } } sub while_loop { my $n = $n; $while_loop_total += $n-- while $n; } sub while_loop2 { use integer; my $n = $n; $while_loop_total2 += $n-- while $n; } __END__ C:\test>junk Rate c_for_loop while_loop while_loop2 foreach_loo +p c_for_loop 4.94/s -- -22% -39% -44 +% while_loop 6.31/s 28% -- -22% -28 +% while_loop2 8.07/s 63% 28% -- -8 +% foreach_loop 8.76/s 77% 39% 8% - +- $foreach_loop_total = 50000050000000 $c_for_loop_total = 50000050000000 $while_loop_total = 50000050000000 $while_loop_total2 = 50000050000000

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