[Haskell-cafe] Why is it so different between 6.12.1 and 6.10.4_1 ?

[Yusaku Hashimoto]

Did you import the module includes the instance of Monad ((->) e)
somewhere in your code loaded in ghci?

I tried this on a fresh ghci 6.12, but I got "No instance" error.

-nwn

On Sat, Mar 27, 2010 at 9:20 AM, zaxis <z_axis at 163.com> wrote:
>
> In 6.12.1 under archlinux
>>let f x y z = x + y + z
>> :t f
> f :: (Num a) => a -> a -> a -> a
>
>> :t (>>=) . f
> (>>=) . f :: (Num a) => a -> ((a -> a) -> a -> b) -> a -> b
>> ((>>=) . f) 1 (\f x -> f x) 2
> 5
>
> In 6.10.4_1 under freebsd
>> let f x y z = x + y + z
> *Money> :t f
> f :: (Num a) => a -> a -> a -> a
>
>> :t (>>=) . f
> (>>=) . f  :: (Monad ((->) a), Num a) => a -> ((a -> a) -> a -> b) -> a -> b
>> ((>>=) . f) 1 (\f x -> f x) 2
>
> <interactive>:1:1:
>    No instance for (Monad ((->) a))
>      arising from a use of `>>=' at <interactive>:1:1-5
>    Possible fix: add an instance declaration for (Monad ((->) a))
>    In the first argument of `(.)', namely `(>>=)'
>    In the expression: ((>>=) . f) 1 (\ f x -> f x) 2
>    In the definition of `it': it = ((>>=) . f) 1 (\ f x -> f x) 2
>
> Sincerely!
>
>
> -----
> fac n = let {  f = foldr (*) 1 [1..n] } in f
> --
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