2013/10/2 Michal Kawalec <michal@bazzle.me>

Excerpts from Karol Samborski's message of 2013-10-02 11:11:15 +0100:

> I think you should just add type signature to the [1..100], like this:
> array (1,100) [(i, i*i) | i <- ([1..100]::[Int])]

Thank you, it seems that it worked, but with my limited knowledge of
Haskell I stumbled onto another problem:

Prelude Data.List Math.FFT Data.Array.CArray Data.Array.Base> array (1,100) [(i, i*i) | i <- [1..100]::[Int]]

<interactive>:74:1:
No instance for (IArray a0 Int) arising from a use of `array'
The type variable `a0' is ambiguous

Possible fix: add a type signature that fixes these type variable(s)
Note: there are several potential instances:

instance Foreign.Storable.Storable e => IArray CArray e
-- Defined in `Data.Array.CArray.Base'
instance IArray Array e -- Defined in `Data.Array.Base'
instance IArray UArray Int -- Defined in `Data.Array.Base'
Possible fix: add an instance declaration for (IArray a0 Int)
In the expression:
array (1, 100) [(i, i * i) | i <- [1 .. 100] :: [Int]]
In an equation for `it':
it = array (1, 100) [(i, i * i) | i <- [1 .. 100] :: [Int]]

--
Michal

This is because ghci doesn't know which instance of IArray to use. If you look at type signature of function 'array' you'll see that it returns some type 'a i e' where 'a e' is an instance of IArray class. So what you must do is simply tell it what 'a i e' you want. Try this:

array (1,100) [(i, i*i) | i <- [1..100]] :: CArray Int Int

Best,
Karol