Here is one trick I have found useful on occasion:
Prelude> :t let f = undefined :: (Num a) => (a,a) -> a in curry f
let f = undefined :: (Num a) => (a,a) -> a in
curry f :: (Num a) => a -> a -> a
undefined (also called bottom) is an element of every type, so if you
just need "something" with a given type, you can write
undefined :: YOUR_TYPE_HERE
If you're having typing troubles in a complex expression, stick in
annotated (i.e. the suffix :: SOME_TYPE) unknowns as placeholders, then
replace them until the type breaks. Use parentheses (undefined :: TYPE)
to be sure, since the binding strength of :: is not high.
PR Stanley wrote:
No, still no idea!
I tried curry f
where f :: (Num a) => (a, a) -> a
and it didn't like it.
For some reason I'm finding this a little chalenging.
Thanks, Paul
At 17:03 03/10/2007, you wrote:
On 10/3/07, PR Stanley
<<mailto:[EMAIL PROTECTED]>[EMAIL PROTECTED]> wrote:
I didn't even know about the curry and uncurry functions. I'm not
looking for the answer but some guidance would be much appreciated.
Thanks, Paul
You can look at the types without seeing the implementation, too. Just
start up GHCI and type:
:t curry
or
:t uncurry
Justin
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