in reply to nondestructive way to look at a character in a string
G'day BernieC,
I would have used index for this (rather than the previously suggested substr).
With index, you are doing exactly what you show in your spec: is the character at a certain position the one you want. With substr, you are extracting a character at a certain position, and then performing a comparison operation.
The amount of coding for both is the same:
$ perl -E ' my @x = qw{ABC DEF BXB}; my ($i, $c) = qw{1 B}; for (@x) { say "$_: ", $i == index($_, $c, $i) ? "YES" : "NO"; say "$_: ", $c eq substr($_, $i, 1) ? "YES" : "NO"; } ' ABC: YES ABC: YES DEF: NO DEF: NO BXB: NO BXB: NO
A Benchmark indicated that index was roughly twice as fast as substr. I used much the same code as I showed above:
#!/usr/bin/env perl use strict; use warnings; use Benchmark 'cmpthese'; my @x = qw{ABC DEF BXB}; my ($i, $c) = qw{1 B}; cmpthese 0 => { index => sub { $i == index($_, $c, $i) ? 1 : 0 for @x }, substr => sub { $c eq substr($_, $i, 1) ? 1 : 0 for @x }, };
I ran this three times. All results were very close. The middle was:
Rate substr index substr 3981142/s -- -46% index 7383385/s 85% --
— Ken
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