[Haskell-cafe] Regular Expression with PCRE

Carter Tazio Schonwald carter.schonwald at gmail.com
Fri Mar 16 23:41:51 CET 2012

have you considered using one of the many amazing HTML parsers on hackage? 

If the goal is to just get the HTML comments, that might be a much more effective use of your time 

Carter Tazio Schonwald

On Friday, March 16, 2012 at 4:55 PM, Joseph Bozeman wrote:

> Hey everyone, I'm hoping someone can point me in the right direction. 
> The regex-pcre package exports (=~) and (=~~) as two useful infix functions. They're great! The only problem is, they are a positive match for a regex. I have a file that contains HTML comments (it was generated in Word) and I really just want the barest text. I already have a function that strips out all the tags, and I have a function that finds all the links and sticks those in another file for later perusal. 
> What I'd like is advice on how to implement the (!~) and (!~~) operators. They should have the same types as (=~) and (=~~). I'm stuck, though. Here's the source for both of those functions: they depend on Text.Rege.PCRE package. 
> (=~) :: (RegexMaker (http://hackage.haskell.org/packages/archive/regex-base/0.93.2/doc/html/Text-Regex-Base-RegexLike.html#t:RegexMaker) Regex (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:Regex) CompOption (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:CompOption) ExecOption (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:ExecOption) source, RegexContext (http://hackage.haskell.org/packages/archive/regex-base/0.93.2/doc/html/Text-Regex-Base-RegexLike.html#t:RegexContext) Regex (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:Regex) source1 target) => source1 -> source -> target 
> (=~) x r = let q :: Regex q = makeRegex r in match q x
> (=~~) :: (RegexMaker (http://hackage.haskell.org/packages/archive/regex-base/0.93.2/doc/html/Text-Regex-Base-RegexLike.html#t:RegexMaker) Regex (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:Regex) CompOption (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:CompOption) ExecOption (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:ExecOption) source, RegexContext (http://hackage.haskell.org/packages/archive/regex-base/0.93.2/doc/html/Text-Regex-Base-RegexLike.html#t:RegexContext) Regex (http://hackage.haskell.org/packages/archive/regex-pcre/0.94.2/doc/html/Text-Regex-PCRE-Wrap.html#t:Regex) source1 target, Monad (http://hackage.haskell.org/packages/archive/base/ m) => source1 -> source -> m target
> (=~~) x r = do (q :: Regex) <- makeRegexM r matchM q x
> What I figured I could do was find a function that was the inverse of "match" and "matchM", but I can't find any in the docs. I really hope I don't have to implement that, too. I'm still new at this, and that seems like it would be over my head.
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