Let say I have a tuple : {:sum, %{x: 23}, %{y: 55 }} Out of this how can I create the following function : def sum({ %{x: 23}, %{y: 55 }} ), do: true as a second question, let say I have : {:sum, %{x: 23}, %{y: 55 }, %{when: “y > 11”} } how do I create the function with guard ? btw. guard form…

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.

I’m trying to make sort of Production system and want header-function-matching to do most of the work for me, where the rules are passed/created from tuples. Btw .. prod system is a list of IF-THEN rules and perfectly match “def fun(IF), do: THEN pattern”

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}…

Why this does not work, but the one you gave work. defmacro rule({ name, goal, work }) do quote do def unquote(name)({ unquote(Macro.escape(goal)), unquote(Macro.escape(work)) }), do: true end end ProdSys.rule({ :test, %{ goal: “test” }, %{} }) ** (ArgumentError) cannot invoke d…

[image] mraptor: Why this does not work, but the one you gave work. What error message do you get and what is the full example code to test with?

here is simpler one : iex(40)> expr = quote do: ProdSys.rule({ :test, 3,5 }) {{:., [], [{:__aliases__, [alias: false], [:ProdSys]}, :rule]}, [], [{:{}, [], [:test, 3, 5]}]} iex(41)> res = Macro.expand_once(expr, __ENV__) {:def, [context: ProdSys, import: Kernel], [{:…

Here is another example : defmodule Test do defmacro rule(namex) do quote do def unquote(namex)() do true end end end @lst [ {:sum, 5, 7 }, {:sum, 1, 3} ] for { name, goal, work } <- @lst do def unquote(name)({ unquote(Macro.escape(goal)), unquote(Macro.escape(work)) }), do: true en…

[image] mraptor: ** (ArgumentError) cannot invoke def/2 outside module That tells you exactly the issue, you are calling rule/1, which is a macro that returns a def AST, and you cannot call def at that location, you can only call it from inside a module. :slight_smile:

So how can I solve it… i.e. be able to create functions on demand !?

[image] mraptor: So how can I solve it… i.e. be able to create functions on demand !? Exactly what the error says, you have to call your rule macro from inside a defmodule body. :slight_smile:

Elixir Programming Language Forum

Create function on-the-fly?

Questions & Help Questions

mraptor January 30, 2018, 9:18pm 14

Yeah I know about erlog , I used it in the past. thanks