小编use*_*988的帖子

我是一个尝试学习haskell的新手,我试图在其他论坛中寻找类似的东西但是找不到类似的问题.

addPoly :: (Num a)=>[[a]]->[a]
addPoly  x = map sum $ transpose x

运行正常

但是当我最后删除x时,它会出错

addPoly :: (Num a)=>[[a]]->[a]
addPoly  = map sum $ transpose 

错误说:

Couldn't match expected type `[[Integer]] -> [Integer]'
            with actual type `[Integer]'
In the expression: map sum $ transpose
In an equation for `addPoly': addPoly = map sum $ transpose

Couldn't match expected type `[[Integer]]'
            with actual type `[[a0]] -> [[a0]]'
In the second argument of `($)', namely `transpose'
In the expression: map sum $ …