我正在尝试定义一个将从列表中删除重复项的函数.到目前为止,我有一个有效的实现:
rmdups :: Eq a => [a] -> [a]
rmdups [] = []
rmdups (x:xs) | x `elem` xs = rmdups xs
| otherwise = x : rmdups xs
但是我想在不使用的情况下重做这件事elem.什么是最好的方法？
我想用我自己的功能而不是nub或者这样做nubBy.
我需要将列表拆分为所有可能元组的列表,但我不确定如何这样做.
例如:
pairs ["cat","dog","mouse"]
应该导致:
[("cat","dog"), ("cat","mouse"), ("dog","cat"), ("dog","mouse"), ("mouse","cat"), ("mouse","dog")]
我能够形成前两个,但我不确定如何得到其余的.
这是我到目前为止所拥有的:
pairs :: [a] -> [(a,a)]
pairs (x:xs) = [(m,n) | m <- [x], n <- xs]