I am trying to write a macro to define a custom operator

  defmacro infix_function(op, function) do
    quote do
      def (a unquote(op) b), do: unquote(function)(a, b)
    end
  end

But I am getting a syntax error on the def (a unquote(op) b) bit. I am not sure if there is an alternative syntax to define operators that would let this work?

As an aside, when pattern matching while writing an operator I am having to do something like this:

  def ((%MyStruct{} = a) * b), do: MyStruct.mult(a, b)

Is there an alternative syntax to defining infix operators that is better suited to pattern matching?