I think it can be unexpected if you're used to other semantics, but the behavior of laziness is very well defined. > let x = [1 .. 100] :: [Int] > seq

I think it can be unexpected if you're used to other semantics, but the behavior of laziness is very well defined. > let x = [1 .. 100] :: [Int] > seq x () -- force the first cons > :sprint x x = 1 : _ -- we evaluated the first cons > foldr (\e l -> e + l) 0 x 5050 -- printing this value forces foldr to complete > :sprint x x = [1,2,3,4,5...100] -- all conses evaluated