tuple and list

tuple_list.ex

defmodule TupleAndListTest do
  @moduledoc false
  use ExUnit.Case
  
  test "tuple cur" do
    '''
    Tuples are most appropriate to group a small,
    fixed number of elements together. When you need a dynamically sized collection, you can use lists.
    '''
    #Bench mark for tuple and list https://aneta-bielska.github.io/blog/benchmarking-elixir-lists-and-tuples-example.html
    #create
    tuple = {"jack",11,"boy"}

    #get Tuple的get操作比较快，o（1）
    assert "jack" == elem(tuple,0)

    #update，update总是有有内存前拷贝
    assert put_elem(tuple,1,12) == {"jack",12,"boy"}

  end

  test "list curd" do
      l1 = [1 |[2 |[3]]]
      #query
      #query is o(n) operation
      '''
      Enum.at is again an O(n) operation: it iterates from the beginning of the list to the desired element.
      Lists are never a good fit when direct access is called for.
      For those purposes, either tuples, maps, or a higher-level data structure is appropriate.
      '''
      assert Enum.at(l1,0) == 1
      assert 1 in l1

      #update will take o(n)
      assert List.replace_at(l1,0,-1) == [-1,2,3]

      #insert will take o(n)，头插最快，没有任何内存消耗和查找，中插（前段：浅拷贝，中间插入新的内存，尾部共享）
      assert List.insert_at(l1,1,4) == [1,4,2,3]
      #insert at end will take n， 尾插最慢，所有前面全部浅拷贝
      assert List.insert_at(l1,-1,4) ==[1,2,3,4]

      #concatenate
      assert [1,2] ++ [3,4] == [1,2,3,4]

      #head
      assert hd([1,2,3]) == 1
      #tail
      assert tl([1,2]) == [2]
      assert tl([1]) == []
  end
end