Question

我有一个Evol类，想要一个distanceMatrix实例应用于我的类型MolSeq列表。函数molseqDistMat按需运行，但我无法理解我在尝试运行distanceMatrix [Molseq]时得到的错误。我理解错误说的是什么，但我无法找到异常。这是错误。

*F2> distanceMatrix l
*** Exception: lab2.hs:79:3-43: Non-exhaustive patterns in function 
distanceMatrix

这是代码。

class Evol a where
  distanceMatrix :: [a] -> [(String, String, Double)]

instance Evol MolSeq where
  distanceMatrix [a] = molseqDistMat [a] [] -- <- Line 79

molseqDistMat :: [MolSeq] -> [(String, String, Double)] -> [(String, 
String, Double)]
molseqDistMat todo res
  | null (tail todo) = res
  | otherwise = molseqDistMat (tail todo) (res++(doRow (head todo) (tail 
todo) []))

doRow :: MolSeq -> [MolSeq] -> [(String, String, Double)] -> [(String, 
String, Double)]
doRow mol rest result
  | null rest = reverse result
  | otherwise = doRow mol (tail rest) ((name mol, name (head rest), 
distance mol (head rest)):result)

Answer 1

你可能想要：

distanceMatrix xs = molseqDistMat xs [] -- <- Line 79

[a]是一个匹配一个元素列表的模式。

Haskell函数中的非穷举模式

1 个答案: