Question

我被要求做一个线上世界的举动。所以我编写了以下代码，（代码中的所有函数都以某种方式在其他模块中定义，所以，不要担心XD，请随时问我是否要查看那些“预定义的函数”）但是当我在终端上运行它时，它显示错误，这是代码：

module Transitions.For_List_2D (
   transition_world -- :: List_2D Cell -> List_2D Cell
) where

import Data.Cell (Cell (Head, Tail, Conductor, Empty))
import Data.Coordinates
import Data.List_2D

transition_world :: List_2D Cell -> List_2D Cell
transition_world world = case world of
    (Head,(x,y)):rest-> (Tail,(x,y)): transition_world rest
    (Tail,(x,y)):rest -> (Conductor, (x, y)): transition_world rest
    (Empty, (x, y)):rest ->(Empty, (x, y)): transition_world rest
    (Conductor, (x, y)):rest
      | element_occurrence==1 || element_occurrence==2 = (Head, (x, y)): transitio
        n_world    rest
      | otherwise = (Conductor, (x, y)): transition_world rest
    [] -> []

然而，当我在终端上通过hs文件的“./”名称运行它时，它显示以下错误：

For_List_2D.hs:23:56: parse error on input '='

我完全被这个错误搞糊涂了提前感谢任何可以帮助我的人。

Answer 1

这些行

  | element_occurrence==1 || element_occurrence==2 = (Head, (x, y)): transition_world    rest
  | otherwise = (Conductor, (x, y)): transition_world rest

应该是

  | element_occurrence==1 || element_occurrence==2 -> (Head, (x, y)): transition_world    rest
  | otherwise -> (Conductor, (x, y)): transition_world rest

我们在方程式（例如函数定义）中使用=，在case表达式中使用->。

我想做一个wireworld移动，但是它显示了一个错误

1 个答案: