Regexp Legibility

I used to (before use strict) compose regexps by hiding the components inside an if, e.g.:

$complex_re = /^($ip) ($host) ($msg)$/ if (
    $ip   = /\d+\.\d+\.\d+\.\d+/,
    $host = /[\-\.\w]+/,
    $msg  = /.*/
);
[download]

Nowadays, I use strict and eval, e.g.

my $complex_re = eval {
    my $ip   = qr/\d+\.\d+\.\d+\.\d+/;
    my $host = qr/[\-\.\w]+/;
    my $msg  = qr/.*/;

    return /^($ip) ($host) ($msg)$/;
);
[download]

We pay about a 5% penalty for the eval when we use this in a tight loop, however we can solve that by moving the regexp creation outside the loop.

                 Rate    with eval without eval
with eval    116279/s           --          -5%
without eval 121951/s           5%           --
[download]

Patrick

Comment on Regexp Legibility Select or Download Code

Replies are listed 'Best First'.
Re: Regexp Legibility by ambrus (Abbot) on Jun 14, 2009 at 14:44 UTC
I think you should use `do {` instead of `eval {` there.	[reply] [d/l] [select]
Re^2: Regexp Legibility by patrickhaller (Initiate) on Jun 21, 2009 at 16:33 UTC
Looks like eval runs faster... `Rate as usual with do as usual 63091/s -- -29% with do 88496/s 40% -- Rate with eval as usual with eval 59773/s -- -9% as usual 65359/s 9% --` [download]	[reply] [d/l]
Re^3: Regexp Legibility by linuxer (Curate) on Jun 21, 2009 at 16:47 UTC
No, it doesn't look like that. In one run "with do" was 40% faster than "as usual", while in the second run, "with eval" iswas 9% slower than "as usual". The "Rate" shows you how many times the specific routine could be run per time unit, so in this case, runs per second. What makes you think, that the eval-solution runs faster? ;) BTW, you can do comparisons with more than two subroutines. So you can do one run and compare all three (or more) routines.	[reply]
Re^3: Regexp Legibility by Anonymous Monk on Jun 21, 2009 at 16:45 UTC
Please show your benchmark code	[reply]


good chemistry is complicated, and a little bit messy -LW
	PerlMonks