[Haskell-cafe] unification would give infinite type

[Emil Axelsson]

Hi,

Depending on what you want, you should either remove 'return' or change to 
'foldM' (from Control.Monad). If you choose the latter, you also need to add a 
type signature to f (because of the monomorphism restriction).

/ Emil



On 2007-12-04 14:43, Rafael wrote:
> Hi... I give this error using hugs for the code:
> 
> ---------------------------------------------------
> f = foldl (\x y -> add x y) 0 [1,2,3]
> add x y = return (x + y)
> ---------------------------------------------------
> I try:
> 
> f = foldl (\x y -> counter x y) (return 0) [1,2,3]
> 
> but it dont solve,  and with ghci:
> 
> "
>     Occurs check: cannot construct the infinite type: b = m b
>       Expected type: b
>       Inferred type: m b
>     In the expression: add x y
>     In a lambda abstraction: \ x y -> add x y
> "
> 
> thnks.
> 
> att
> Rafael
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