use Perl

• custom sorting (Score:1)

  by link (3402) on 2005.01.27 17:07 (#37846) Homepage Journal

  By custom sorting do you mean passing your own sorting method into the package method? Is this some restriction with the module itself or just a question of speed? perlfunc -f sort says if you prototype your sort method you can have it called as a proper sub,slower but depending on your data size it might not be much of an issue for you.

  use A;
  
  sub strange($$)
  {
          return -1 if $_[0] == 3;
          return 1 if $_[1] == 3;
          return $_[0] <=> $_[1];
  }
  
  A::try(\&strange)
  
  package A;
  
  sub try
  {
          my ( $method ) = (@_);
          my @A = sort $method ( 1 , 2 ,3 ,4 ,5 );
          print join(",",@A) . "\n";
  }
  1;

  Reply to This

  • Re:custom sorting (Score:1)

    by osfameron (3135)

    thanks - I came up with using @_ arguments last night (though I initially did {$func->($a,$b)} until I read the perlfunc entry about prototyping ($$).

    A benchmark of a simple sort on 1000 rows done over 10 million iterations shows a small ( Of course once you start like this, and realize you can create sort libraries you end up by creating complex sorts (like: "sort first by Jan/Feb/Mar order in one column, THEN by numeric order in another") with function composition, which does start to add some overhe

    --
    

    osfameron
    • (oops) Re:custom sorting (Score:1)

      by osfameron (3135)

      Hmm, can't seem to edit that comment, once more, with preview! thanks - I came up with using @_ arguments last night (though I initially did {$func->($a,$b)} until I read the perlfunc entry about prototyping ($$).

      A benchmark of a simple sort on 1000 rows done over 10 million iterations shows a small (<10%) variation, bizarrely favouring the @_ version despite the extra level of indirection... I think that deciding you can't support custom sorting because using the overhead of @_ over $a,$b is too g

      --
      

      osfameron