How does match? function work in kernel.ex

gusaiani · November 7, 2016, 10:20pm

Wondering how match? does what it does, does anyone know of an explanation, or can anyone walk me through the code?

elixir-lang/elixir/blob/master/lib/elixir/lib/kernel.ex#L2293



    :match ->
      invalid_match!(:is_struct)

    :guard ->
      quote do
        is_map(unquote(term)) and
          (is_atom(unquote(name)) or :fail) and
          :erlang.is_map_key(:__struct__, unquote(term)) and
          :erlang.map_get(:__struct__, unquote(term)) == unquote(name)
      end
  end
end

@doc """
Gets a value from a nested structure.

Uses the `Access` module to traverse the structures
according to the given `keys`, unless the `key` is a
function, which is detailed in a later section.

Thanks!

OvermindDL1 · November 7, 2016, 10:32pm

Basically it just converts this:

result = match?(a, b)

Into this:

result =
  case b do
    a ->
      true
    _ ->
      false
  end

So it just tests if the left argument matches the right argument via a case expression, and if it does it returns true, if it does not then it returns false.

gusaiani · November 7, 2016, 10:52pm

Thanks, OvermindDL1.

Got it.