What does "&1" mean in elixir function?

Question

Given this function, what does &1 refer to?

Enum.map [1, 2, 3, 4], &(&1 * 2)

Answer 1

&1 refers to the first argument the callback function would receive. The ampersand by itself (&) is a shorthand for a captured function. This is how you could expand that function.

Enum.map([1, 2, 3, 4], fn x -> x * 2 end)

fn -> is equal to &(...

x -> x is equal to ...(&1

A quick reference can be found here