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sml中的mutual recursion

admin 1月 30, 2021 0

在ML中使用and连接两个相互调用的函数，这样不会出现找不到定义的情况。

fun match xs =
  let fun s_need_one xs =
        case xs of
            []=>true
          | 1::xs' => s_need_two xs'
          | _ => false
      and s_need_two xs =
          case xs of
              []=>false
            | 2::xs' => s_need_one xs'
            | _ => false
  in
      s_need_one xs
  end