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Today I had to write a regular expression definitely more complex than I'm used to do (I'm a real inept: for example this is the first time I use x modifier in REs :)).

This experience showed me I spent a lot of time trying to make my RE working, specially (in my opinion) 'cause I'm not able to debug it in a good way.

I used some tecniques in order to make my work faster (well, I should say "not so slow"...):

  • x modifier. I think the first debug trick is always avoid debug, i.e. write correct code :). And to write correct RE a good trick is comprehend what are you writing. Whitespaces and comments are very good and, last but not least, they let you...
  • proceed incrementally. I wrote my code incrementally, commenting large chunks of the regular expression and debugging only small pieces
I guess there are other tricks of ways to code better and faster (faster! faster than before... :)), like:
  • prepare case tests instead of using only actual data that will be processed by the RE.
  • exploit the isomorphism between RE and state machines. Did you ever simulated by hand your RE (I mean, a "real" RE) using paper, pencil, coins and drawing a state machine? (and using a computer?
  • I'd really like to discover there's a way to follow what's happening at "core level" when Perl try to satisfy a RE. This is not very good from my point of view (I think this kind of "insight" perturbs what's happening at core level), but I also think that such a possibility should save me some time this afternoon. Maybe something like this?

What do you think about?


In reply to Debugging regular expressions by larsen

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