Hello All, Sorry about my previous post, email was hosed. I was working on a homework problem where the task is to write the iterate function in terms of scanl. Came up with this: myIterate f x = scanl (const.f) x (repeat x) I went looking around for other solutions to check my work and found the following solution on the Haskell Wiki: iterate f x = scanl f x (repeat x) myIterate seems to work checked against the Prelude iterate but I don't know if it's a good solution or not, because the iterate solution on the Haskell Wiki throws a type error. Types of Prelude iterate and scanl are different, so I can see why, or am I missing something? Here is some REPL output: Prelude iterate: λ> take 10 (iterate (+1) 1) [1,2,3,4,5,6,7,8,9,10] myIterate: λ> take 10 (myIterate (+1) 1) [1,2,3,4,5,6,7,8,9,10] Haskell Wiki solution: λ> take 10 (iterate' (+1) 1) error: • Occurs check: cannot construct the infinite type: a ~ a -> a Expected type: a -> a -> a Actual type: (a -> a) -> a -> a • In the first argument of ‘iterate'’, namely ‘(+ 1)’ In the second argument of ‘take’, namely ‘(iterate' (+ 1) 1)’ In the expression: take 10 (iterate' (+ 1) 1) • Relevant bindings include it :: [a] (bound at <interactive>:63:1) It will work if you pass it a function that takes two parameters though: λ> take 10 (iterate' (+) 1) [1,2,3,4,5,6,7,8,9,10] Any thoughts would be much appreciated! Andrea