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Re: Regex Homework

by Boots111 (Hermit)
on Feb 24, 2004 at 22:28 UTC ( [id://331540]=note: print w/replies, xml ) Need Help??


in reply to Regex Homework

chyleto1~

You appear to have a solution to problem (1), although I have not thoroughly checked it myself. For problem 2 I would advise breaking it down into smaller chunks.

Let us say hypothetically that I had a regular expression R that matched all strings with an even number of as. How would I modify it to match an odd number of as? How would I modify it to match an even number of bs? How would I glue these results together?

The trick I usualy find most helpful for deriving new regular expressions is to start at the ends (or just the left) and work toward the middle. It is also useful to have a set of stock expression that one knows will match certain things (like even numbers of a particular character). That way I can glue these basic blocks together via alternation (|).

Hope that helps,
Boots
---
Computer science is merely the post-Turing decline of formal systems theory.
--???

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