小编use*_*706的帖子

以下编译没有警告或错误.

factors n = [x | x<-[1..n], n `mod` x == 0]
perfects n = [x | x <- [1..n], x == sum (factors (init x))]
main = putStrLn "hello"

即使我犯了错误.

perfects n = [x | x <- [1..n], x == sum (factors (init x))]  -- incorrect
perfects n = [x | x <- [1..n], x == sum (init (factors x))]  -- should have been

静态类型检查在哪里进行救援？

我认为应该抓住错误的原因是:

• factor显然期望一个Integral因为它的参数使用mod,而init返回aList
• 更何况x从绘制List …