[Haskell-cafe] monadic parser with Happy and Alex

[Duncan Coutts]

On Sat, 2008-10-04 at 17:05 +0200, Manlio Perillo wrote:
> Hi.
> 
> I have completed a draft of a CSS lexer, using Alex.
> http://hg.mperillo.ath.cx/haskell/webtools/file/tip/src/CSS/Lexer.x
> 
> The lexer use the posn wrapper.
> 
> Now I'm starting to write the parser with Happy, however for the final 
> product I would like to:
> 1) Be able to do I/O in the lexer, for stylesheets inclusion
>     (@import rule)
> 2) be able to keep state in the parser (or lexer?), for character
>     transcoding (@charset rule)
> 
> 
> This should be possible with Happy (and there are some example), however 
>   I don't find examples that make use of a lexer written with Alex.

See c2hs or Language.C it uses a monadic lexer.

Duncan