Dinko Tenev wrote:
On 5/31/05, Daniel Fischer <[EMAIL PROTECTED]> wrote:
Why is ghc unable the determine the type of the Literal 0 in the
definition of g?
Answer: Since somewhere an instance e.g. New [(a,Double)] (Map a Int)
could be defined, leading to problems when threating 0 as (0::Int).
There could be such an instance, but that's obviously not the case.
At the point where g is defined, GHC only knows about New [(a,b)] (Map
a b), and New [(a,Double)] (Map a Int) doesn't fit.
Consider this:
*Main> :type new . flip zip [0..]
new . flip zip [0..] :: (New [(a, b1)] b, Num b1, Enum b1) => [a] -> b
Trying to infer
New [(u, v)] w
out of all that we know, i.e.
New [(a,b)] (Map a b)
should give us
w === Map u v --->
New [(u, v)] (Map u v)
so finally
v === Int --->
New [(u, Int)] (Map u Int)
to infer the context of g.
Is there any good reason not to do this?
Because I'm not smart enough to understand it?
;-)
Cheers,
D. Tenev
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