Builtin regex (Was: How to complex switch?)

[Dmitry Olshansky]

On 13.05.2011 18:25, Robert Clipsham wrote:
> On 13/05/2011 05:14, Ary Manzana wrote:
>> How about making regex a built-in feature with this syntax: /regex/ ?
>>
>> I didn't use regex a lot before I started using Ruby. The thing is, in
>> Ruby it's so easy to use regex that I just started using them a lot more
>> than before. Of course, ruby has built-in operators for matching regexs,
>> so maybe that should also be added to the language (it's the =~
>> operator, but in D it should be a different one.)
>
> Regex is ugly, impossible to maintain/debug and slow for anything 
> mildly complicated - a handwritten parser is magnitudes faster, and 
> easy to understand, maintain and debug. If it's simple, you may as 
> well write a couple of extra lines and have it be a lot faster.
>

Handwritten parser is faster, but hard to get right, port or maintain. 
Also handwritten parser has almost zero flexibility - patching it to 
accommodate new kinds of input is PITA.
Regexes on the other hand are widely known DSL for pattern matching, 
which IMO easier to get right, port across languages and platforms (with 
caveats). Flexibility - regex engines in a way are just simple parser 
generators with some bells and whistles. And BTW they could be quite 
fast (depending on the use case, of course).

> Just my opinion of course, I know you're bound to disagree :>
>

Probably you never faced problems like "get me some info from these 
<enter your gazillon number> simple reports/emails/etc." All things that 
don't follow some formal language enjoy flexibility on the parser side. 
E.g. you can patch together through try/trial cycle a couple of 
aproximate regexes and have very reasonable results in no time.

The real pitfall of regexes vs handcrafted parsers is that they can't 
match important classes of problems like: "the innermost parenthesized 
expression in a given string" and such.

-- 
Dmitry Olshansky