Data Structures

Syntax#

• [head | tail] = [1, 2, 3, true] # one can use pattern matching to break up cons cells. This assigns head to 1 and tail to [2, 3, true]

• %{d: val} = %{d: 1, e: true} # this assigns val to 1; no variable d is created because the d on the lhs is really just a symbol that is used to create the pattern %{:d => _} (note that hash rocket notation allows one to have non-symbols as keys for maps just like in ruby)

Remarks#

As for which data structure to us here are some brief remarks.

If you need an array data structure if you’re going to be doing a lot of writing use lists. If instead you are going to be doing a lot of read you should use tuples.

As for maps they are just simply how you do key value stores.

Lists

a = [1, 2, 3, true]

Note that these are stored in memory as linked lists. Id est this is a series of cons cells where the head (List.hd/1) is the value of first item of the list and the tail (List.tail/1) is the value of the rest of the list.

List.hd(a) = 1
List.tl(a) = [2, 3, true]

Tuples

b = {:ok, 1, 2}

Tuples are the equivalent of arrays in other languages. They are stored contiguously in memory.