A quick Benchmark will show that this repeated concatenation is slower than sprintf:
#!/usr/local/bin/perl

use Benchmark;


my $var=13;
my $length=6;

timethese(100000, {
 CONCAT=>\&concat,
 SPRINTF=>\&spr_f,
});

sub concat {
 my $a = $var;
 while (length($a)<$length) {$a="0$a";}
}

sub spr_f {
 my $a = $var;
 sprintf("%0$length", $a);
}

Results:
Benchmark: timing 100000 iterations of CONCAT, SPRINTF...
    CONCAT:  2 wallclock secs ( 1.53 usr +  0.00 sys =  1.53 CPU) @ 65
+359.48/s (n=100000)
   SPRINTF:  0 wallclock secs ( 0.60 usr +  0.00 sys =  0.60 CPU) @ 16
+6666.67/s (n=100000)

[download]
UpdateOops, fixed the bug, tye's right that it doesn't change the result much, but I didn't really want to return the correct value in concat() or make spr_f() extra fast, just wanted to compare the process to create the desired result.

In reply to Re: Re: Zero Padding by runrig
in thread Zero Padding by Anonymous Monk

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