How to split a list of strings into given number of lists in erlang -

given list , integer, want split list specified number of lists (inside list).

for example:

input:

[1,2,3,4,5,6,7,8,9], 3 

output:

[[1,2,3],[4,5,6],[7,8,9]] 

what clean , efficient way this?

the solution written steve vinoski calls length/1 in guard each partition makes o(n^2). bothers me because can done in o(n) , performance freak. can done in many ways example there one:

divide(l, n) when is_integer(n), n > 0 ->     divide(n, 0, l, []).  divide(_, _, [], acc) ->     [lists:reverse(acc)]; divide(n, n, l, acc) ->     [lists:reverse(acc) | divide(n, 0, l, [])]; divide(n, x, [h|t], acc) ->     divide(n, x+1, t, [h|acc]). 

or modification of steve's solution

divide(l, n) ->     divide(l, n, []).  divide([], _, acc) ->     lists:reverse(acc); divide(l, n, acc) ->     try lists:split(n, l) of         {h,t} -> divide(t, n, [h|acc])     catch         error:badarg ->             lists:reverse([l|acc])     end. 

or simpler:

divide([], _) -> []; divide(l, n) ->     try lists:split(n, l) of         {h,t} -> [h|divide(t, n)]     catch         error:badarg -> [l]     end.