Re: [boost] Re: Announcing: xpressive

From: Beman Dawes (bdawes_at_[hidden])
Date: 2003-11-19 12:09:21

At 12:19 AM 11/18/2003, Joel de Guzman wrote:

 >Eric Niebler <eric_at_[hidden]> wrote:
 >> Brian McNamara wrote:
 >>
 >>> I agree that it is desirable to be able to _statically_ (at
 >>> compile-time) analyze and "compute on" regexps.
 >>>
 >>> The main disadvantage is that it forces us to write regexps "ugly":
 >>>
 >>>    +(_1 = "hello ") >> "world"
 >>>
 >>> rather than "pretty":
 >>>
 >>>    regexp("(hello )+world")
 >>
 >> Some would say regular expressions are ugly any way you look at them.
 >> :-) As an expression template, you can use whitespace, indenting and
 >> comments to make your regular expression more readable. Beauty is in 
the
 >> eye of coder.
 >
 >Same here. I dislike REs a lot. It gives me a mild headache whenever I 
have
 >to read understand one. "(hello )+world" is ok--It's the more complex 
stuff
 >that gives me an eye strain. For instance, from the regex manual:
 > "\\A(\\d{3,4})[- ]?(\\d{4})[- ]?(\\d{4})[- ]?(\\d{4})\\z". I really hate 

 >those escapes. I also hate the fact that you can't format the code and
 >sprinkle it with whitespace. The ugliness of the RE syntax is one of the
 >motivating forces that made me write Spirit.

While I agree with you about the escapes, it really isn't correct that "you 
can't format the code and sprinkle it with whitespace".

To take your example:

   "\\A(\\d{3,4})[- ]"  // first group comment
   "?(\\d{4})[- ]"      // second group comment
   "?(\\d{4})[- ]"      // third group comment
   "?(\\d{4})\\z"       // fourth and final group comment

C++'s adjacent string concatenation rule (2.13.4/3) is very helpful in 
making any long string literal more readable. Not just RE's.

--Beman