From: Ross Bamford <rossrt@...>
Date: 2006-03-10T20:50:16+09:00
Subject: Re: Small regexp question

On Fri, 2006-03-10 at 19:58 +0900, francisrammeloo@hotmail.com wrote:
> Hi all,
> 
> I am writing some refactoring code for a C++ project.
> 
> I need to change:
> 
>      class MyClass
>      {
>       ...
>      }
> 
> to:
> 
>      class IMP_EXP MyClass
>     {
>      ...
>     }
> 
> The pattern I used to find a class definition line is:
> 
>     line =~ /^\s*class\s+(\w+)/
> 
> But I want to exclude forward class declarations ( class MyClass; )
> 
> So I changed my pattern to:
> 
>     line =~ /^\s*class\s+(\w+)\s*[^;]/    --> don't match if line ends
> with ";"
> 
> But it doesn't work... Why?

Your regexp is trying to match:

	+ zero or more spaces
	+ the word 'class'
	+ one or more spaces
	+ one or more word characters (captured)
	+ zero or more spaces
	+ any single character except ';'

By the time you get to that ';' there likely won't be any input left, so
no character to be something except ';'. You could do it with lookahead,
but it's probably easier to do:

	"class MyClass;" =~ /class\s+(\w+)[^;]*$/
	# => nil

	"class MyClass" =~ /class\s+(\w+)[^;]*$/
	# => 0

	"class MyClass {" =~ /class\s+(\w+)[^;]*$/
	# => 0

	"class MyClass { /* etc */ }" =~ /class\s+(\w+)[^;]*$/
	# => 0

There are probably still things this will miss though. For example,
strange class names could well result in a failure to match...

-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk