[Haskell-cafe] Permutations

[Miguel Mitrofanov]

import Data.List
eqPerms [] = [[]]
eqPerms xs = [x:xt | x <- nub xs, xt <- eqPerms $ delete x xs]

On 30 Nov 2008, at 18:03, Andrew Coppin wrote:

> OK, so here's something just for fun:
>
> Given a list of items, find all possible *unique* permutations of  
> that list. (E.g., the input list is explicitly _allowed_ to contain  
> duplicates. The output list should not contain any duplicate  
> permutations.)
>
> I've found one simple way to do this, but I'm sure there are  
> multiple valid approaches. So let's see what people come up with. ;-)
>
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