[Haskell-cafe] Intersection types for Haskell?
Brian Hulley
brianh at metamilk.com
Wed Jan 11 11:54:34 EST 2006
David Menendez wrote:
> Brian Hulley writes:
>
>> Also, as a second point, could functional dependencies in type
>> classes be written using a similar syntax eg instead of
>>
>> class Insert t c a | c a -> t where
>> insert :: t -> c a -> c a
>>
>> we could write:
>>
>> class Insert (h (c a)) c a where
>> insert :: h (c a) -> c a -> c a
> <snip>
> Your example, in the syntax of associated type synonyms, would look
> something like this:
>
> class Insert c a where
> type T c a
> insert :: T c a -> c a -> c a
Thanks for the link. I suppose h(c a) can't be used on its own because h is
assumed to be a tycon rather than a general type function, but if this
restriction were lifted, the syntax "h a" meaning "some type determined by a
by the type function h" could be used both for intersection typing and
multi-param type classes.
Regards, Brian.
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