[erlang-questions] No Namespace for Macros

Zoltan Lajos Kis <>
Thu Oct 15 20:04:35 CEST 2009


Hello,

You could stick to name your macros as modulename_macroname.

%%%%valueHouse.hrl
-define(valueHouse_Value, 10).
%%%%valueCar.hrl
-define(valueCar_Value, 2).


star(X) ->
       case X of house -> ?valueHouse_Value;
                       car -> ?valueCar_Value
        end.


Regards,
Zoltan.

sapan shah wrote:
> 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
>
>   



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