Hi -
I've got the following function which doesn't compile:
createMonoMultiFont
:: (MonadException m, Enum i, Bounded i)
=> [(i, Font, Colour)] -> m (MonoMultiFont i)
createMonoMultiFont elements =
liftIO . block $ do
mmfRaw <- duma_MonoMultiFont_create (fromEnum (maxBound::i))
mmfPtr <- newForeignPtr duma_MonoMultiFont_Release mmfRaw
return $ MonoMultiFont mmfPtr
The problem is that ghc complains that there is no instance for Bounded i
even though I've written "Bounded i" in the type declaration for the
function.
I was expecting that I could use the same type variables in the function
body as in the type signature so that I could use maxBound::i to find the
max bound of whatever type is instantiated to i.
What am I doing wrong here, and is it possible to create such a function?
Thanks, Brian.
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