Macro Question

times.exs

# Exercise: MacrosAndCodeEvaluation-2
# Write a macro called *times_n* that takes a single numeric argument. It should define a function 
# called *times_n* in the caller's module that itself takes a single argument, and that multiplies 
# the argument by *n*. So, calling *times_n(3)* should create a function called *times_3*, and 
# calling *times_3(4)* should return 12. Here's an example of it in use:
# 
# defmodule Test do
#   require Times
#   Times.times_n(3)
#   Times.times_n(4)
# end
#
# IO.puts Test.times_3(4) #=> 12
# IO.puts Test.times_4(5) #=> 20
#

defmodule Times do
  defmacro times_n(n) do
    func_name = "times_#{n}"

    quote do
      def unquote(func_name)(x) do
        x * unquote(n)
      end
    end
  end
end

defmodule Test do
  require Times
  Times.times_n(3) # CompileError: invalid syntax in def "times_3"(x)
end

Changing the line:

func_name = "times_#{n}"

to:

func_name = String.to_atom("times_#{n}")

Resolves the CompileError. This makes sense now that I think about it because the macro was essentially generating:

def "times_3"(x) do

If I understand correctly, function names are implicitly defined atoms, hence why start_link functions support parameters like (MyModule, :func).