It works, but the evaluation order won’t entirely match the “Ruby blocks” intuition, especially when things like else get involved:

defmodule DoTest do
  def foo(do: x, else: y) do
    IO.inspect({x, y}, label: "in foo")
  end
end

DoTest.foo do
  IO.puts("in do")
else
  IO.puts("in else")
end

## prints:
# in do
# in else
# in foo: {:ok, :ok}

The parser makes the transformation from do ... end to do: ... consistently, but plain def always evaluates arguments (versus defmacro which passes arguments as AST)

Welcome to the forum!

It’s not possible to define a function that does this. You can define a macro that does this, but the behaviour is extremely different to the behaviour in Ruby.

To achieve what you’ve described you would use an anonymous function:

test fn ->
  puts("sup there")
end

This is conceptually the same as a block/proc in Ruby.

Perhaps this also approximates what you are looking for?

def test(do: block)
 block
end

test do
 puts("sup there")
end