Re: Pattern matching bug

[Roberto Ierusalimschy <roberto@...>]

> Consider the following patterns:
> "(%w+)=([\"'])([^%2]-)%2"
> "([\"'])([^%1]-)%1"
> 
> If the first pattern is applied against the following strings:
> 1) "key1='value1'"
> 2) "key2='value2'"
> 
> It will match #1 and not #2.  Similarly, for the 2nd pattern, if it is
> applied against those same two strings, it will match #2, and not #1.
> 
> The trouble is in the sequence "([^%2]-)" which should be
> "non-greedily match anything except the characters contained in
> capture 2".
> It appears that is actually doing "non-greedily match anything except
> the characters contained in capture 2 and the actual number 2".
> 
> Thoughts?  I have already found a workaround, but this pattern is
> syntactically valid, it just doesn't work in the expected manner.  I
> took a look through lstrlib.c, but it was not immediately obvious
> where the problem might be.

It does not work the mannter you expect, but it does what the manual
says it does.  The "%2" you want is a 'pattern item', but there are no
items inside character classes. Inside a class the '%' only escapes
characters.

-- Roberto