From: Andrew Stewart <boss@...>
Date: 2007-12-14T21:58:46+09:00
Subject: Re: Regexp Matching Not Blank And Not A Specific Word?


On 13 Dec 2007, at 19:09, Phrogz wrote:

> On Dec 13, 11:16 am, Andrew Stewart <b...@airbladesoftware.com> wrote:
>> Hi,
>>
>> Please could somebody show me how to write a regular expression that
>> matches when the input is not blank and it's not a specific word,
>> e.g. dog.
>>
>> For example, I would hope for these results:
>>
>> '' =~ regexp       # nil
>> 'dog' =~ regexp    # nil
>> 'cat' =~ regexp    # not nil
>
>
> irb(main):006:0> tests = [ "", "dog", "cat", "doggone it" ]
> => ["", "dog", "cat", "doggone it"]
>
> irb(main):007:0> tests.each do |str|
> irb(main):008:1*   hit = (str =~ /^(?!dog).+$|^dog.+$/)
> irb(main):009:1>   puts "#{str.inspect} => #{hit.inspect}"
> irb(main):010:1> end
> "" => nil
> "dog" => nil
> "cat" => 0
> "doggone it" => 0

That's fantastic, thank you!

When I was trying this yesterday, I think I failed to appreciate that  
(?!re) doesn't consume the match.  Now I know.

Thanks also for the tip in your previous email about Ruby 1.8 and  
lookbehinds.

Regards,
Andy Stewart

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