假设我有一个排序算法和两个自定义比较器：
mySort :: [[Int]] -> ([Int] -> [Int] -> Ordering) -> [[Int]]
mySort = undefined
myCmp1 :: [Int] -> [Int] -> Ordering
myCmp1 xs ys
| a0 < b0 = LT
| a0 > b0 = GT
| a1 < b1 = LT
| a1 > b1 = GT
| a1 == b1 = EQ where
a0 = head xs
b0 = head ys
a1 = last xs
b1 = last ys
myCmp2 :: [Int] -> [Int] -> Ordering
myCmp2 xs ys
| a0 > b0 = LT
| a0 < b0 = GT
| a1 > b1 = LT
| a1 < b1 = GT
| a1 == b1 = EQ where
a0 = head xs
b0 = head ys
a1 = last xs
b1 = last ys
有什么方法可以定义类型签名，[Int] -> [Int] -> Ordering以便我可以像这样使用它？
comparator = [Int] -> [Int] -> Ordering
mySort :: [[Int]] -> comparator -> [[Int]]
mySort = undefined
这是类型别名的作用：
type Comparator = [Int] -> [Int] -> Ordering
他们也可以接受以下论点：
type Comparator a = a -> a -> Ordering
然后你可以写，例如
mySort :: Comparator a -> [a] -> [a]
本文收集自互联网，转载请注明来源。
如有侵权，请联系[email protected] 删除。
我来说两句