On 06/09/10 11:23, Johannes Waldmann wrote:
We have overloaded numerical literals (Num.fromInteger)
and we can overload string literals (IsString.fromString),
so how about using list syntax ( [], : )
for anything list-like (e.g., Data.Sequence)?
I would have thought you have two obvious choices for the type-class
(things like folding are irrelevant to overloading list literals):
class IsList f where
fromList :: [a] -> f a
or:
class IsList f where
cons :: a -> f a -> f a
empty :: f a
I'd go for the first, as I'd imagine you are only overloading the
[a,b,c] form, not the a:b:c:[] form, and the first reflects this
better. Both of these could be used to convert a list literal into a
list-like type (e.g. Sequence). But neither of them would be useful for
sets or maps, because the classes lack an Ord constraint on the type a
-- maybe this makes overloaded list literals fairly limited in utility.
Thanks,
Neil.
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