无法匹配预期的类型

Question

我有以下Haskell程序:

catlines = unlines . zipWith (\(n,l) -> show n ++ l) [0..]

main = putStrLn $ catlines ["A", "B"]

当我尝试编译它时,GHC给出以下错误:

catlines.hs:1:41:
    Couldn't match expected type `b0 -> String' with actual type `[a0]'
    In the expression: show n ++ l
    In the first argument of `zipWith', namely
      `(\ (n, l) -> show n ++ l)'
    In the second argument of `(.)', namely
      `zipWith (\ (n, l) -> show n ++ l) [0 .. ]'

据我所知,这应该编译.我不知道出了什么问题.

Answer 1

问题是传递给的函数zipWith应该采用两个参数,而不是元组.试试这样:

zipWith (\n l -> show n ++ l)