Re: [Haskell-cafe] laziness blowup exercise

On Tue, Jul 14, 2009 at 6:02 PM, Thomas Hartman wrote:

myiterate f x =  let nxt = f x  in nxt `seq` x : myiterate f nxt

iterate' f x = x `seq` x : iterate' f (f x) seems better; it doesn't evaluate list elements you don't visit.

let test = 1 : 2 : 3 : undefined in last $ take 4 $ myiterate (test !!) 0 *** Exception: Prelude.undefined

let test = 1 : 2 : 3 : undefined in last $ take 4 $ iterate' (test!!) 0 3

-- ryan