让声明错误

Question

我有以下haskell语句的问题:

insertSort3 xs =
    let sort3 [] ys = ys
         sort3 (x:xs) ys = sort3 xs (insert x ys)
    in sort3 xs []

我的编译器说:在输入'='上解析错误(错误发生在第三行).

Answer 1

问题是第二行中的缩进let:

insertSort3 xs = 
 let sort3 [] ys = ys
     -- the next line should line up with the previous sort3
     sort3 (x:xs) ys = sort3 xs (insert x ys)
 in sort3 xs []