[REBOL] Re: Parse versus Regular Expressions
From: joel:neely:fedex at: 4-Apr-2003 17:28
Hi, Gabriele,
Gabriele Santilli wrote:
> JN> 1) It makes the PARSE dialect a strange hybrid between declarative
> JN> and procedural descriptions (as mentioned in my earlier post).
>
> The PARSE dialect is something that is matched to the input string
> or block from left to right. I'm not sure if this makes it an
> hybrid; probably it does, and I admit I like it this way. (Much
> better than RE, that is.)
>
My point (regarding declarative-vs-procedural) was simply that RE
notation purely describes the pattern one is looking for, and the
RE engine manages all the complexity for you, *including* the cases
where backtracking is necessary to find a complete match after a
false start. It appears to me that PARSE requires the programmer to
do more work when backtracking may be needed.
The specific example at hand required the programmer to take action
to make the first alternative fail before PARSE would consider the
second. It would be nice if failure at the end of the *entire* rule
also caused backtracking so the programmer didn't have to do any
extra work.
-jn-
--
----------------------------------------------------------------------
Joel Neely joelDOTneelyATfedexDOTcom 901-263-4446
Counting lines of code is to software development as
counting bricks is to urban development.
