From: Andrew Stewart <boss@...>
Date: 2008-01-17T01:52:29+09:00
Subject: Re: regular expression


On 16 Jan 2008, at 15:57, Johnathan Smith wrote:
> i wanting to write a regular expression which matches words which
> contain the vowels [aeiou] in alphabetical order
>
> im not sure where to start so any help would be greatly appreciated

This will get you started:

IRB:
 >> re = /[^aeiou]*[a][^aeiou]*[e][^aeiou]*[i][^aeiou]*[o][^aeiou]*[u] 
[^aeiou]*/
=> [aeiou][a][aeiou][e][aeiou][i][aeiou][o][aeiou][u][aeiou]
 >> 'abstemious' =~ re
=> 0
 >> 'facetious' =~ re
=> 0
 >> 'bstemious' =~ re
=> nil
 >> 'ebstamious' =~ re
=> nil

You can see there's a lot of repetition in the regular expression so  
the next step would probably be to DRY it.  I leave that as an  
exercise to the reader (because I can't work out how to do it :)

You'll may also wish to anchor the regular expression so it doesn't  
cross words.

Regards,
Andy Stewart

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