[Haskell-cafe] annoying output

[Philip Weaver]

I mean powers of *ten* :)

On Dec 8, 2007 10:48 PM, Philip Weaver <philip.weaver at gmail.com> wrote:

> Well, you're choosing to parse each digit of your integer as a separate
> integer, so if you want to combine them after reading you'll need to
> multiply by powers of two.  Or, you can just read in all the digits in one
> 'read' command, like this:
>
>    parseInt :: String -> (Expr, String)
>    parseInt xs = let (digits, rest) = span isDigit
>                        in (EInt (read digits), rest)
>
> where 'span' is defined in the Prelude.  Hope this helps!
>
> - Phil
>
> On Dec 8, 2007 10:03 PM, Ryan Bloor <ryanbloor at hotmail.com> wrote:
>
> > hi
> >
> > The code below does almost what I want but not quite! It outputs...parseInt
> > "12444a"         gives...
> > [(EInt 1,"2444a"),(EInt 2,"444a"),(EInt 4,"44a"),(EInt 4,"4a"),(EInt
> > 4,"a")]
> >
> > What I want is: [(EInt 12444, "a")]
> >
> > data Expr = EInt {vInt :: Int} -- integer values
> >  | EBool {vBool :: Bool} -- boolean values
> >
> > parseInt :: Parser
> > parseInt (x:xs)
> >  | (isDigit x && xs /= []) = [(EInt (read [x]),xs)] ++ parseInt xs
> >  | isDigit x && xs == [] = [(EInt (read [x]),[])]
> >  | otherwise = []
> >
> > Thanks
> >
> > Ryan
> >
> >
> >
> >
> >
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