From: Robert Brown <[EMAIL PROTECTED]>
> Casey West writes:
> > : "Does the regular expression mechanism in perl optimize regular >
> : expressions such as the one you used earlier in this thread so that
> > : the execution overhead is nearly as good as the C approach I
> outlined > : earlier in this thread? In other words, for the problem
> stated > : earlier, does o(C) = o(perl)? > > The answer is, C almost
> always going to be much faster almost all the > time, YMMV. Really
> the only way to tell is with tests and benchmarks, > but you can
> almost always bet on C.
>
> Sorry again for my confusing way of expressing myself. Although I
> wrote my example in C, that was because I am a novice perl programmer,
> but an experienced C programmer, so I expressed my algorithm in C.
>
> The idea was to compare the execution effeciency of a perl regular
> expression approach to a less syntacticly compact algorithmic approach
> using loops and conditionals, still written in perl, to edit the
> string. I just used C so you all would not beat me up over perl
> syntax details instead of answering the real question.
>
> Is perl going to be comparably efficient whichever way you code it, or
> is the explicit test and loop approach usually going to be faster for
> simple jobs? I want to know when to use the regex approach and when
> not to.
1. Perl builtins and especialy the regular expression engine is
heavily optimized. So it might very well be quicker to use a regexp
from Perl than to implement the same stuff in C. Unless you spend a
lot of time tweaking the code.
2. One regexp (assuming its created well) will almost always be
quicker than several loops and ifs in Perl.
While you should not use a regexp where the "normal" functions
suffice, you should not go into great lengths implementing something
that would be simple as a regexp. It'll be harder to maintain and
most probably slower.
3. If you really need to know which solution is quicker
use Benchmark;
Jenda
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