[Haskell-beginners] how to feel free of the Implementation of Data structure
markus.l2ll at gmail.com
Fri Mar 25 11:17:15 CET 2011
There's also ListLike: http://hackage.haskell.org/package/ListLike
On Fri, Mar 25, 2011 at 6:32 AM, 吴兴博 <wuxb45 at gmail.com> wrote:
> :) Thanks.
> 2011/3/24 Brent Yorgey <byorgey at seas.upenn.edu>:
> > On Thu, Mar 24, 2011 at 06:34:57PM +0800, 吴兴博 wrote:
> >> 2.
> >> f1 :: (Integral a) => a -> String
> >> f2 :: (Integral a) => String -> a
> >> pipe = f1 . f2
> >> It is clear that pipe is String -> String,
> > Actually, this code will give an "ambiguous type" error, since the
> > compiler cannot figure out what type 'a' should be. And the type that
> > is chosen may make a difference for the behavior.
> >> but.(1)How can I know what instance that 'a' is.
> >> (2)How can I determine what instance of 'a' is.
> > If you know what type you want to use for 'a' you can specify it with
> > a type annotation, like this:
> > pipe = f1 . (f2 :: String -> Int)
> > -Brent
> > _______________________________________________
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> > Beginners at haskell.org
> > http://www.haskell.org/mailman/listinfo/beginners
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