No Namespace for Macros

sapan shah <>
Thu Oct 15 07:54:43 CEST 2009


Hi,

Erlang does have the concept of namespace for the functions( we do
lists:map(...))
Why does it not have this concept for macros?

Consider this scenario: I have an application which deals with the value of
some things. (lets say a house & a car)
So, I define macros in two different files for the things.
%%%%valueHouse.hrl
-define(Value, 10).
%%%%valueCar.hrl
-define(Value, 2).

Now, My application file could be something like this
%%%application.erl
-module(application).
-include("valueHouse.hrl").
-include("valueCar.hrl").  %% This will not compile... ll give 'redefining
macro error'... assume it is allowed in erlang

star(X) ->
       case X of house -> ?valueHouse:Value;
                       car -> ?valueCar:Value
        end.
%%%%%%%%%%%%%%%%%%

This is just a cooked up example. One may have this kind of need in a big
application.
For exapmle, Java supports this (public static final variables).

Any Explanation?????

Regards,
Sapan Shah


More information about the erlang-questions mailing list