RE: bugs in happy

> I tried to write a monadic lexer and parser just to find that:
> 
> - omitting %name defaults to happyParse. However this name is used 
> internally in a different function at a different location, 
> leading to a 
> "Multiply declarations of `Parser.happyParse'" error form 
> GHC. It doesn't 
> change if I give any of the -a -c -g flags.

True, thanks for pointing it out.

> - the documentation on the web is outdated (version 1.11)

The version number is incorrect, the docs are really for version 1.13.

> - the documentation for monadic parsers (Section 2.5) says 
> that the type 
> for happyError is [Token] -> P a which I naively believed. 
> It's P a. Later 
> in the example you deceptively suggest to define
> 
> happyError tokens = failE "Parse error"
> 
> but, as above, there are not tokens.

If you specify %lexer as well as %monad, then the type of happyError
becomes P a.  I suspect this is what you're doing.

Cheers,
        Simon