我正在通过阅读"又一个Haskell教程"这本书来学习haskell,而且当谈到contiuation传递风格时我遇到了一个问题.这本书给出了一个cps折叠:
cfold’ f z [] = z
cfold’ f z (x:xs) = f x z (\y -> cfold’ f y xs)
并给出测试结果:
CPS> cfold (+) 0 [1,2,3,4]
10
CPS> cfold (:) [] [1,2,3]
[1,2,3]
但是,当我尝试测试时,我发现存在问题,ghci给出:
*Main> cfold (+) 0 []
<interactive>:8:7:
Occurs check: cannot construct the infinite type:
t10 = (t10 -> t10) -> t10
Expected type: t10 -> t10 -> (t10 -> t10) -> t10
Actual type: t10 -> t10 -> t10
In the first argument of `cfold', namely …haskell ×1