How do I find the array element directly preceeding a 'match'?

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: How do I find the array element directly preceeding a 'match'? by amelinda (Friar) on Oct 13, 2000 at 03:30 UTC
Try this: `foreach $item (@array) { if (matches($item)) { $found = $last; last; } $last = $item; }` [download] where `$last` holds the "preceeding list element" of the current item and `$found` holds the "preceeding list element" of the item that matches.	[reply] [d/l] [select]
Re: How do I find the array element directly preceeding a 'match'? by ton (Friar) on Apr 05, 2001 at 03:39 UTC
Or you could just use a for loop, and eliminate the need for multiple assignments: `for ($i=0; $i<scalar(@array); ++$i) { last if (matches($array[$i])); } $found = $array[$i-1] if ($i);` [download]	[reply] [d/l]
Re: How do I find the array element directly preceeding a by Fastolfe (Vicar) on Oct 13, 2000 at 00:49 UTC
The "correct" solution is to iterate through the indexes, not the elements themselves: `for ($i = 0; $i < @array; $i++) { if (matches($array[$i])) { $found = $array[$i-1]; } }` [download] If you want to insist doing it in foreach style: `foreach $item (@array) { if (matches($item)) { $found = $last; } $last = $item; }` [download] Originally posted as a Categorized Answer.	[reply] [d/l] [select]
Re: How do I find the array element directly preceeding a by merlyn (Sage) on Oct 13, 2000 at 10:46 UTC
`for ($i = 0; $i < @array; $i++) { if (matches($array[$i])) { $found = $array[$i-1]; } }` [download] Ugh. What if `$i = 0` at the match? You've just indexed into the end of the array? Either start at 1, or redefine your problem for the unusual case. Originally posted as a Categorized Answer.	[reply] [d/l]