On 5/31/05, robert dockins
Dinko Tenev wrote:
First we observe that, g = new . flip zip [0..], so, without the type specification, it has the general type (New [(a, b1)] b, Num b1, Enum b1) => [a] -> b, as reported by GHC.
Then we infer from
(1) g :: (New [(u, v)] w, Num v, Enum v) => [u] -> w
and
(2) instance New [(a, b)] (Map a b)
that in (New [(u, v)] w), w can only be (Map u v)
This step in the reasoning requires a functional dependency, which you mentioned earlier you were unwilling to supply. Without functional dependencies w can, in fact, be something other than (Map u v).
We need to infer New [(u, v)] w, and the only thing we know so far is New [(a, b)] (Map a b). In this context, what else could we possibly have for w besides (Map u v) ? Cheers, D. Tenev