in reply to The nth occurrence of a character

Does no one use index() anymore?!? 

#!/usr/bin/perl

use warnings; use strict;

sub find_nth {
   my ($s,$c,$n) = @_;
   my $pos = -1;
   while ($n--) {
      $pos = index($s,$c,$pos+1);
      return -1 if $pos == -1;
   }
   return $pos;
}

my $str="Now is the time for all good men to come to the aid of their 
+country";
my $n = 5;
my $c = "o";

print find_nth($str,$c,$n), "\n";

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I'll leave it to those people who like to benchmark to decide whether or not this is an "efficient Perl function" :-)

duff

Replies are listed 'Best First'.
Re^2: The nth occurrence of a character
by duff (Parson) on Feb 09, 2006 at 06:07 UTC

    Ah well, in a fit of boredom I decided to benchmark the submissions myself. The results are unsurprising (at least to me).

    Read more... (4 kB)

    Here are some results on my system; the first set of benchmarks are for multple occurences in one string, the second set is for a single occurence in multiple strings: 

                  Rate RoyJohnson      salva       duff    mickeyn
RoyJohnson   373/s         --       -86%       -97%       -98%
salva       2604/s       598%         --       -78%       -88%
duff       11887/s      3089%       357%         --       -44%
mickeyn    21159/s      5576%       713%        78%         --
              Rate RoyJohnson      salva    mickeyn       duff
RoyJohnson 15272/s         --        -9%       -42%       -48%
salva      16847/s        10%         --       -36%       -42%
mickeyn    26298/s        72%        56%         --       -10%
duff       29202/s        91%        73%        11%         --

    duff

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