[erlang-questions] Sets from list then to list?

Kostis Sagonas <>
Mon Apr 7 10:51:46 CEST 2008


Alexander Lamb wrote:
> Hello (list:-)
> 
> Using list comprehension, I am building a list of tuples that I want  
> unique and sorted.
> 
> Is this a correct way of doing it:
> 
> Result = sets:to_list(sets:from_list([ {A,B} || {_X,_Y,A,_Z,B} <-  
> MyList]))
> 
> Then sort the Result.
> 
> The alternative would be to use one of the lists functions to copy  
> elements into a new list and testing first at each insert if the  
> element is already present.
> 
> What is best?

None of the two.  Check out lists:usort/1.

1> lists:usort([{1,2},{1,3},{0,1},{1,2}]).
[{0,1},{1,2},{1,3}]


Kostis



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