Re: One line assigment statement with regex match

in reply to One line assigment statement with regex match

If the words in @terms are litterals, you could try:

($match) = grep { $lineFromSomeFile =~ $_ } @terms;
[download]

Paul

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Re^2: One line assigment statement with regex match by tlm (Prior) on Jun 23, 2005 at 00:31 UTC
When looking for short literals, `index` is more efficient than a regex: `my @matches = grep index( $lineFromSomeFile, $_ ) > -1, @terms;` [download] Update: Added the link and the qualifier "short" in response to kaif's comment++. How short is short? When I tested random (but constant) strings and substrings of lengths 80 and 8, respectively, which are "typical" lengths for a line and a word, `index` was about 20% faster than the corresponding regex. I imagine that it is this sort of analysis that's responsible for the widespread reputation of `index` as being superior to regexes. Clearly, as kaif shows, the ratio of speeds is sensitive to the sizes of the string and the substring being searched, but I have not done a detailed analysis beyond this, and what is posted in the node linked above. the lowliest monk	[reply] [d/l]
Re^3: One line assigment statement with regex match by kaif (Friar) on Jun 23, 2005 at 01:59 UTC
So, a lot of people like to say that. And indeed, sometimes `index` is ten times faster. But sometimes it's more than three times slower! use Benchmark qw(:all); $text = <<EOF; aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +aaaaaaaaaa EOF $pattern = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"; cmpthese($count, { 'regex' => sub { $text =~ $pattern }, 'index' => sub { index $text, $pattern }, }); __DATA__ Rate index regex index 630601/s -- -67% regex 1914815/s 204% -- [download] Moreover, increasing the lengths of the text and pattern, I can make the regex be 40 times faster. See Re^8: "advanced" Perl functions and maintainability for reasons why people use regexes instead of `index`. Personally, I still don't understand why there even is a difference in speed -- shouldn't the regex engine be optimized to notice that this is a search for a constant string and then call the same function as `index`? : No, I'm not kidding. The output follows. Moreover, for this example, adding a single `study $text` is an extra 10 times faster, completely obliterating `index`. `Rate index regex study index 178/s -- -98% -100% regex 7538/s 4124% -- -92% study 98871/s 55311% 1212% --` [download] Update: I'm running perl v5.8.5 built for i686-linux.	[reply] [d/l] [select]
Re^2: One line assigment statement with regex match by ketema (Scribe) on Jun 22, 2005 at 22:04 UTC
This statement works fine. Thank You.	[reply]

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