[Haskell-cafe] Automatic derivation (TemplateHaskell?)

[Joel Reymont]

Shouldn't this work just as well?

numExpr =
     choice [ try $ float >>= return . Num
            , integer >>= return . Int
            ]

It works on "Foo(10.345)" but not on "Bar(10, 103.34)".

On Apr 5, 2007, at 4:09 PM, Stefan O'Rear wrote:

>> numExpr :: GenParser Char a NumExpr
>> numExpr = do sg <- lexeme sign
>>              nf <- natOrFloat
>>              return $ either (Int . sg) (Nat . sg) nf
>
> It seems silly that there is no signed version of natOrFloat
> predefined, any Parsec experts?
>
> Stefan

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