[Haskell] How to substract a list?

[Trevion]

On Mon, 28 Mar 2005 01:53:39 +0200, Pierre Barbier de Reuille
<pierre.barbier at cirad.fr> wrote:
> ([1..10]++[1..10]) \\ [3..6]
> [1,2,7,8,9,10,1,2,7,8,9,10]
> 
> So _all_ the elements with values in [3..6] where removed !!
> If that's what you want ! Perfect ... if not : what do you want exactly
> ? List substraction is not uniq.

This is what I would have expected as well; however, the definition of
(\\) in the report uses delete, which only removes the first occurence
of each element in the second list from the first.  GHC 6.2.2 uses
that behavior as well, so:

Prelude Data.List> ([1..10] ++ [1..10]) \\ [3..6]
[1,2,7,8,9,10,1,2,3,4,5,6,7,8,9,10]

  .trev

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