Just guessing. How do you know it's an accident? Richard O'Keefe wrote:

On 15 Jun 2009, at 4:26 pm, Tony Morris wrote:

...

Prelude Data.List> nub . concat $ [[2, 3], [1, 2], [2, 3, 4], [1, 2, 3]] [2,3,1,4]

In this particular case. But that's a lucky accident.\

-- Tony Morris http://tmorris.net/