Approach for constants shared between modules in Elixir

constants.ex

defmodule Constants do
  @moduledoc """
  An alternative to use @constant_name value approach to defined reusable 
  constants in elixir. 

  This module offers an approach to define these in a
  module that can be shared with other modules. They are implemented with 
  macros so they can be used in guards and matches

  ## Examples: 

  Create a module to define your shared constants

      defmodule MyConstants do
        use Constants

        define something,   10
        define another,     20
      end

  Use the constants

      defmodule MyModule do
        require MyConstants
        alias MyConstants, as: Const

        def myfunc(item) when item == Const.something, do: Const.something + 5
        def myfunc(item) when item == Const.another, do: Const.another
      end

  """
  
 defmacro __using__(_opts) do
    quote do
      import Constants
    end
  end

  @doc "Define a constant"
  defmacro constant(name, value) do
    quote do
      defmacro unquote(name), do: unquote(value)
    end
  end

  @doc "Define a constant. An alias for constant"
  defmacro define(name, value) do
    quote do
      constant unquote(name), unquote(value)
    end
  end
end

Perfect. Thank you :)

This generally works fine:
defmacro constant(name, value) do
quote do
defmacro unquote(name), do: unquote(value)
end
end

But if you use it in some other context, like for example this:

for {name, value} <- [ some_list_of_name_value_pairs ] do
constant(name, value)
end

I get a problem because it doesn't work with variables bound from the environment, at least not in elixir 1.3.4

I have a modified version that works for me:

defmacro constant(key, entry) do
quote bind_quoted: [key: key, entry: entry] do
def unquote(key)() do
unquote(entry)
end
end
end

This ties values from the caller environment into the definition... IIRC. Anyway - for my purposes that version worked better.

66666666