Simple things should be coded simply (Re: Idiomatic Array Index Search?)

Notes:

A hash is useful for multiple look-ups, since you have to realize that the CREATION of the hash is going to require a look at the entire array.
grep is going to go through your entire array, and "jumping" out of grep isn't a "nice" thing to do.

That said, I would take an approach like:

# prototype here for "look and feel good"ness
# if you remove it, be sure to pass array by
# reference (this is done for speed reasons)

# $index = get_index @array, $element;

sub get_index (\@$) {
  my ($a, $e) = @_;
  my $i = 0;
  for (@$a) { return $i if $e eq $_; $i++; }
  return -1;
}
[download]

There's no reason to get more idiomatic, because it will cloud the meaning of your code. The most simple things should be coded simply.

japhy -- Perl and Regex Hacker

Comment on Simple things should be coded simply (Re: Idiomatic Array Index Search?) Download Code

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Re: Simple things should be coded simply (Re: Idiomatic Array Index Search?) by merlyn (Sage) on May 28, 2001 at 20:33 UTC
`sub get_index (\@$) { my ($a, $e) = @_; my $i = 0; for (@$a) { return $i if $e eq $_; $i++; } return -1; }` [download] I don't like code like this because you've got two things in that loop that are being kept in sync only coincidentally: the iteration of the foreach, and the incrementing of the index. I'd let there be one thing, and use the indirection to ensure consistency: `sub get_index (\@$) { my ($a, $e) = @_; for (my $i = 0; $i <= $#$a; $i++) { return $i if $e eq $a->[$i]; } return -1; }` [download] This is clearer to me. Simple things should be coded simply. {grin} -- Randal L. Schwartz, Perl hacker	[reply] [d/l] [select]
Re: Simple things should be coded simply (Re: Idiomatic Array Index Search?) by mattr (Curate) on May 28, 2001 at 18:57 UTC
I agree with all the above (simple things simple etc.) but am wondering what happens if you have two matching elements. I don't remember anybody saying they were unique, and an array just looks like a set when you use qw() but it isn't one mathematically. So maybe you should return an array, sorted of course. Then may I propose the most idiomatic would be to use another language, SQL of course? I am thinking of DBD::RAM. You could say something like `print $dbh->selectcol_arrayref(qq [ SELECT phrase FROM my_phrases WHERE id = 1 ORDER BY phrase ])->[0];` [download] Some other neat looking modules may include Search::InvertedIndex, Search::Binary, and Math::IntervalSearch (Search where an element lies in a list of sorted elements). ..to answer japhy and merlyn below, honored to join this thread with you both. To be sure, grep is good. Thank you for your elegant code.	[reply] [d/l]
Re: Re: Simple things should be coded simply (Re: Idiomatic Array Index Search?) by japhy (Canon) on May 28, 2001 at 19:21 UTC
Then `grep()` would be a super choice: `sub get_index { my ($a, $e) = @_; my @idx = grep $a->[$_] eq $e, 0 .. $#$a; return wantarray ? @idx : $idx[0]; }` [download] `japhy` -- Perl and Regex Hacker	[reply] [d/l]