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Re: [Try-out] Regexp do's and don'ts

by Dietz (Curate)
on Aug 15, 2004 at 09:56 UTC ( #383071=note: print w/replies, xml ) Need Help??


in reply to Regexp do's and don'ts

5. Do know what your regex really means.<br> Do know about ^, $, variable interpolation, the matching rules as de +scribed by the Camel Book, modifiers, and the meaning of \n (newline) + in combination with ., ^ and $
Do know about precedence since disregarding it is one of the highest crime in regex country:

I've made a sample common mistake not paying attention to precedence and I use this as a chance to pillory myself giving a perfect example of what not to do.

In node Re: Short or Long Hand I was using an alternation being based on anchors:

/^0|6$/
This simply says match 0 at the beginning or match 6 at the end while my intention was to match 0 or 6 ranging from beginning to the end of the string:
/^(?:0|6)$/

As an addition to your tutorial I'd like to see the basic requirement for regexes:
You can't write an efficient regex as long as you don't know what your expected data will be:
Always think of the expected data while changing or simplifying regexes.

I personally like the term 'regexpected'
Keep it in mind and it will save your life ;-)

Please feel free to downvote node Re: Short or Long Hand
/me castigating myself for not paying attention to precedence

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