https://happi.github.io/theBeamBook/ is a good resource for looking at the internals of how the BEAM itself works. Decisions and capabilities like the one you’re describing are gonna either be present or absent on the basis of the BEAM itself, Elixir just gets compiled to BEAM byte code.

@jgonet There are not many cases in which you actually touch the Erlang/BEAM low-level stuff directly or have to keep them in mind (most of the time, Elixir’s abstractions are very leak-free). However, I would recommend watching Solid Ground because it will give you a good high-level foundation of understanding what trade-offs have been made in Erlang/BEAM .

There are no function pointers in elixir.

&+/2 is different in every module you write this. Also, even though both of the following functions are obviously producing the same result for their respective domains, you can’t computationally compare them for equality without doing manual prooves:

def multiply_a(a, b), do: a * b

def multiply_b(0, _), do: 0
def multiply_b(_, 0), do: 0
def multiply_b(1, b), do: b
def multiply_b(a, b) when a > 0, do: b + multiply(a - 1, b)
def multiply_b(a, b) when a < 0, do: multiply(-a, -b)

Both of these functions are “equal” to */2, but for the latter it will be very hard to proof in a language like elixir.

Just rewrite your dispatcher to use atoms (or accept all functions with arity 2).

def f(op, [a, b | s]) when op in [:+, :-, :*, :/], do: [apply(:erlang, op, [a, b]) | s]
def f(v, s) when is_number(v), do: [v | s]

def g(op, [a, b | s]) when is_function(op, 2), do: [op.(a, b) | s]
def g(v, s), do: [v | s]