Cetin Sert wrote:
class Streamable a where
to :: a -> Stream a
The type of to looks wrong for me. a -> Stream a means to takes a single
element into a stream of such elements, but you probably want to convert
between different representations of streams of elements.
toStream :: [a] -> Stream a
instance Streamable [a] where
to = toStream -- ERROR: see below
Here to :: [a] -> Stream [a] and toStream :: [a] -> Stream a. These
types are different, as ghc complained.
Possible solutions include multi parameter type classes
class Streamable s a where
to :: s -> Stream a
instance Streamable [a] a where
to = toStream
and constructor classes
class Streamable s where
to :: s a -> Stream a
instance Streamable [] where
to = toStream
Tillmann
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