[Haskell-cafe] ANN: TextRegexLazy-0.56, (=~) and (=~~) are here

[Chris Kuklewicz]

Bulat Ziganshin wrote:
> Hello Chris,
> 
> Wednesday, August 2, 2006, 3:16:58 PM, you wrote:
> 
>> Announcing: TextRegexLazy version 0.56
> 
> your feature list is really strong! it will be great now to make it
> a part of GHC standard distribution
> 
> afaiu, selection of regex engine implemented via import statements?
> 

You can actually choose which backend (=~) uses at runtime:

> {-# OPTIONS_GHC -fglasgow-exts #-}
> import Text.Regex.Lazy
> 
> import qualified Text.Regex.PCRE as R
> import qualified Text.Regex.PosixRE as S
> import qualified Text.Regex.Full as F
> 
> -- Choose which library to use depending on presence of PCRE library
> 
> (=~) :: (RegexMaker R.Regex R.CompOption R.ExecOption a,RegexContext R.Regex b t
>         ,RegexMaker F.Regex F.CompOption F.ExecOption a,RegexContext F.Regex b t
>         ,RegexMaker S.Regex S.CompOption S.ExecOption a,RegexContext S.Regex b t)
 >      => b -> a -> t
> (=~) = case R.getVersion of
>          Just _ -> (R.=~)
>          Nothing -> case S.getVersion of
>                       Just _ -> (S.=~)
>                       Nothing -> (F.=~)
> 
> main = print (("ba" =~ "(.)a") :: (String,String,String,[String]))

The R.getVersion and S.getVersion detect whether it was compiled against PCRE or 
PosixRE.  The (=~) is then chosen at run time.