I was working on a Question which was ,

Input - A list of numbers - [1,2,3,4,5] example

We have to produce the subsets of this list and display those subsets whose sum is equal to 10

Output Format - [ [1,2] , [2,3] , [4,5,6] ] example

Means we have to append those subset in a list whose sum is 10 and make a nested list and print it as an output.

here is my code ..

defmodule Combination do
  def combine([]) do
    []
  end
  def combine([head | tail]) do
    tail_combinations = combine(tail)
    merged_combinations = Enum.map(
      [[]] ++ tail_combinations,
      fn c -> c ++ [head] end
    )
    tail_combinations ++ merged_combinations
  end

#Main thing I am doing here, i am Checking the sum of the subsets but unable to append the list of subset into another list and print the final list

  def display(lis) do
    a=[]
    for vale <- Combination.combine(lis) do
      if Enum.sum(vale)==6 do
        a=a++[vale]
      end
    end
    IO.inspect(a)
  end
end
Combination.display([1,2,3,4])

Error :

erts@eyrc:~/fr_task0_9999/.vscode$ elixir practice.exs
warning: variable "a" is unused (if the variable is not meant to be used, prefix it with an underscore)
  practice.exs:17: Combination.display/1

[]
erts@eyrc:~/fr_task0_9999/.vscode$ 

Can anyone help me i am new to elixir and i got stuct at this point.
Tell me how can i append the list in another list and print the whole list at once .

thank you