Dne 28.5.2013 12:32, Johannes Waldmann napsal(a):
Jose A. Lopes <jose.lopes <at> ist.utl.pt> writes:
unionWith :: Ord k => (a -> b -> c) -> Map k a -> Map
k b -> Map k c
what should be the result of
unionWith undefined (M.singleton False 42) (M.singleton True "bar") ?
Perhaps the generalized signature should be instead:
```haskell
unionWith :: Ord k => (Maybe a -> Maybe b -> c) -> Map k a -> Map k b ->
Map k c
```
(The function would always get at least one `Just`.)
But this functionality can be achieved using `map`s and the current
`unionWith`.
P.P.
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