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% --
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