[Haskell-cafe] Is it possible to print out types of instances in
jeremy.shaw at linspireinc.com
Sun Jan 16 13:07:14 EST 2005
At Sun, 16 Jan 2005 12:09:43 +0100,
> On Sun, 16 Jan 2005 00:13:08 -0800, Jeremy Shaw
> <jeremy.shaw at linspireinc.com> wrote:
> > Hello,
> > Is it possible to write a function that would display all the instances
> > of a class currently in scope?
> > For example, for 'Show a' it should output something like:
> > The instances of 'Show a' currently in scope are:
> > Show Int
> > Show Float
> > Show Char
> > Show ...
> In GHC 6.3:
> Prelude> :i Show
> class Show a where
> showsPrec :: Int -> a -> String -> String
> show :: a -> String
> showList :: [a] -> String -> String
> -- Imported from `GHC.Show'
> instance Show IOMode -- Imported from `GHC.IOBase'
> instance Show IOException -- Imported from `GHC.IOBase'
> instance Show IOErrorType -- Imported from `GHC.IOBase'
> instance Show HandleType -- Imported from `GHC.IOBase'
Neat! Is there some way I can get access to that information from
within my program ? Maybe something like:
instancesOf :: Name -> [Type]
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