Create function on-the-fly?

Here’s a simple example using your data that might get you started:

defmodule Gen do
  @fun_list [
    {:sum, %{x: 23}, %{y: 55 }}
  ]
  
  for {fun, a, b} <- @fun_list do
    def unquote(fun)(unquote(Macro.escape(a)), unquote(Macro.escape(b))), do: true
  end
end

In IEx:

iex(3)> Gen.sum(%{x: 23}, %{y: 55 })                                                      
true

Can you talk a bit more about your use case?

Elixir macros can generate functions at compile time from data but this is a bit of an odd way to go about it. If you’re trying to do it at run time I think you really just need to treat it as a data transformation instead of as meta-programming.

What error message do you get and what is the full example code to test with?