功能跟踪中的非穷举模式'

Question

trace :: String -> Float -> Colour -> [ColouredLine]  
trace (c:cs) angle colour  
 = trace' (c:cs) angle colour (0.0,0.0)  
  where  
   trace' "" angle colour intvertex = []  
   trace' (c:cs) angle colour intvertex  
       | c == 'R' = trace' cs (angle-90) colour intvertex  
       | c == 'L' = trace' cs (angle+90) colour intvertex  
       | c == 'F' = [(intvertex,aftvertex,colour)] ++ trace' cs angle colour aftvertex  
         where  
           aftvertex = fst (move 'F' (intvertex,angle) angle) 

REPORT：

  

trace“F [RF] [LF] [FF]”45.0（1.0,0.0,0.0）=异常：LSystems.hs：（95,4） - （101,61）：函数跟踪中的非穷举模式“

预期的测试用例：

  

[（（ - 8.742278e-8,2.0），（ - 1.3113416e-7,3.0），（1.0,0.0,0.0）），（（ - 4.371139e-8,1.0），（ - 0.7071068,1.7071068 ），（1.0,0.0,0.0）），（（ - 4.371139e-8,1.0），（ - 8.742278e-8,2.0），（1.0,0.0,0.0）），（（ - 4.371139e-8,1.0 ），（0.7071067,1.7071068），（1.0,0.0,0.0）），（（0.0,0.0），（ - 4.371139e-8,1.0），（1.0,0.0,0.0））]

Answer 1

您的测试字符串包含'['和']'，但您只匹配模式匹配中的'R'，'L'和'F'。所以一旦达到方括号，你就会得到一个例外。