[Haskell-cafe] Re: Parsec : Problems with operator precedence (solution)

[Benedikt Huber]

Erik de Castro Lopo schrieb:
> Erik de Castro Lopo wrote:
> 
>>     binaryOp :: String -> (SourcePos -> a -> a -> a) -> E.Assoc -> E.Operator Char st a
>>     binaryOp name con assoc =
>>         E.Infix (reservedOp name >>
>>             getPosition >>=
>>             return . con) assoc
> 
> Replacing reservedOp above with:
> 
>     reservedOpNf :: String -> CharParser st ()
>     reservedOpNf name = try (reservedOp name >> notFollowedBy (oneOf "|&="))
> 
> fixed the problem.
> 
Hi Erik,
There is an easy, better solution, modifying the lexer:

 > lexer = makeTokenParser $ emptyDef
 >           { L.reservedOpNames = words "&& || & | ^" }
 > reservedOp = P.reservedOp lexer
 > identifier = P.identifier lexer
 > ...

I'd try to avoid 'try', if possible.

benedikt