[Haskell-cafe] unification would give infinite type

[Rafael]

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