[Haskell-cafe] I need a hint in list processing

[Fernan Bolando]

On Sun, Jun 14, 2009 at 4:13 PM, Erik de Castro
Lopo<mle+hs at mega-nerd.com> wrote:
> Fernan Bolando wrote:
>
>> Hi all
>>
>> If I have a number of list
>> example
>> list1 = [2,3]
>> list2 = [1,2]
>> list3 = [2,3,4]
>> list4 = [1,2,3]
>>
>> I want to create a list from the list above with n elements,
>> non-repeating and each elements index represents 1 of the elements
>> from the corresponding list so for the above input I would get.
>>
>> a = [3,2,4,1]
>>
>> ofcourse there may be several set that will satisfy the problem, so a
>> list of list that satisfies would be good.
>>
>> How do I do this in haskell? or is there a code snippet that seems to
>> work similarly?
>
> Well you could simply concatenate all the lists using the (++) operator
> and then use Data.List.nub:
>
>    http://haskell.org/ghc/docs/latest/html/libraries/base/Data-List.html#v:nub
>
> to remove duplicates.
>
Using Data.List.nub
Data.List> nub [2,3,1,2,2,3,4,1,2,3]
[2,3,1,4]

that is not exactly what I want. list1 only has 2,3 has elements and list2 only
has elements 1,2...this means the first element should only be 2 or 3 and
the second element should only have 1 or 2...etc

fernan
-- 
http://www.fernski.com