9 Apr
2008
9 Apr
'08
5:04 a.m.
However, I have this feeling that
bar :: forall a . Id a -> String
with a type family Id *is* parametric in the sense that no matter what a is, the result always has to be the same. Intuitively, that's because we may not "pattern match on the branch" of a definition like
type instance Id String = .. type instance Id Int = .. ..
But in a degenerate case there could be just this one instance: type instance Id x = GADT x which then reduces this example to the GADT case of which you said that is was "clearly parametric". Tom -- Tom Schrijvers Department of Computer Science K.U. Leuven Celestijnenlaan 200A B-3001 Heverlee Belgium tel: +32 16 327544 e-mail: tom.schrijvers@cs.kuleuven.be url: http://www.cs.kuleuven.be/~toms/