hashNub package:witherable

hashNub :: (Witherable t, Eq a, Hashable a) => t a -> t a
witherable Witherable
Removes duplicate elements from a list, keeping only the first occurrence. This is usually faster than ordNub, especially for things that have a slow comparison (like String). 
>>> hashNub [3,2,1,3,2,1]
[3,2,1]
hashNubOn :: (Witherable t, Eq b, Hashable b) => (a -> b) -> t a -> t a
witherable Witherable
The hashNubOn function behaves just like hashNub, except it uses a another type to determine equivalence classes. 
>>> hashNubOn fst [(True, 'x'), (False, 'y'), (True, 'z')]
[(True,'x'),(False,'y')]