•Re: Re: Text::ParseWords regex doesn't work when text is too long? (fixes)

Unless they did something recently to radically break backward compatibility, [^\1\\] means "anything except a control-A or a backslash".

In other words, in the words of the Inigo Montoya in Princess Bride, "I don't think that means what you think that means".

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

Update: verified that:

"\1" =~ /[^\1]/
[download]

fails, while

"\1X" =~ /[^\1]/
[download]

succeeds in Perl 5.8, validating my original hypothesis at least for the latest public Perl release.

Comment on •Re: Re: Text::ParseWords regex doesn't work when text is too long? (fixes) Select or Download Code

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regex bottom line? by edan (Curate) on May 12, 2003 at 09:58 UTC
So, assuming that I'll need to roll my own `parse_line` by modifying the regex... what regex will provide the same functionality but work for arbitrarily large strings? Since I still don't really understand what `/(?!\1)[^\\]/` does, I am having trouble with this... I reason that it should match anything that's not a quote (whichever quote was opened at the start of the match), but I don't see how it does this... Should I use tye's first regex? I also don't get how `/((?:\\.\|[^'"\\]+\|(?!\1)['"])*)/` works... Does `/[^'"\\]+\|(?!\1)['"]/` do the same thing as `/(?!\1)[^\\]/` ? -- 3dan	[reply] [d/l] [select]
Re: regex bottom line? (bottom method) by tye (Sage) on May 12, 2003 at 16:13 UTC
The only method that supports arbitrary strings is the last one, as I demonstrated. Does `/[^'"\\]+\|(?!\1)['"]/` [download] do the same thing as `/(?!\1)[^\\]/` [download] ? No. But `/[^'"\\]\|(?!\1)['"]/` (note that I removed the "+") and `/(?!\1)[^\\]/` are the same (provided \1 is either `"'"` or `'"'`). That is, they each match a single character that is not a backslash (\), nor the same as the quote character in \1. Since the regex is matching zero or more occurrences of X or Y or Z, it also works to match zero or more occurrences of X or Y+ or Z. Replacing Y with Y+ means we can grab tons of "uninteresting" characters quickly so that we don't have to loop through the surrounding `(?: ... )*` so many times (since we've seen that we are only allowed to loop through it 32k times). - tye	[reply] [d/l] [select]