list - haskell 列表中的唯一元素

Question

好吧，这可能是前奏，但是:是否有一个标准库函数可以查找列表中的唯一元素？为了澄清起见，我的(重新)实现是:

has :: (Eq a) => [a] -> a -> Bool
has [] _ = False
has (x:xs) a
  | x == a    = True
  | otherwise = has xs a

unique :: (Eq a) => [a] -> [a]
unique [] = []
unique (x:xs)
  | has xs x  = unique xs
  | otherwise = x : unique xs

Answer 1

我在 Hoogle 上搜索了 (Eq a) => [a] -> [a] .

第一个结果是 nub (从列表中删除重复元素)。

胡格尔太棒了。