Compile time executable calling?

[Daniel Kozak]

On Friday, 12 July 2013 at 22:46:39 UTC, Justin Whear wrote:
> On Sat, 13 Jul 2013 00:36:21 +0200, Peter Alexander wrote:
>
>> On Friday, 12 July 2013 at 20:42:50 UTC, Tofu Ninja wrote:
>>> So I had an idea recently, wouldn't it be cool to have the 
>>> ability to
>>> call an executable at compile time and capture its output.
>> 
>> How long until D compilers are able to read mail? :-)
>> 
>> There's many obvious applications of this proposed feature, 
>> but I say
>> such things should be delegated to the build process. Just run 
>> those
>> executables using a makefile, or whatever build system you use.
>> 
>> If you need compile time inputs from your D code then just run 
>> a
>> separate build to extract them. Yes it's more work and less 
>> convenient,
>> but I think we need to be careful with how much is added to 
>> the D
>> compilers. We don't want to turn them into operating systems.
>
> Other compilers allow symbols/macros to be defined on the 
> command line,
> e.g. gcc's `-D` flag;  it'd be nice for DMD to define a similar 
> mechanism
> for defining enums, e.g.
>
> ---D code---
>   void main() { writeln(VERSION_NUMBER); }
> ------------
>
> dmd main.d -DVERSION_NUMBER=1.2
>
> Currently I have to use my makefiles to output a whole file 
> which defines
> the various build constants.

A few minutes ago, I have a same issue. I need add some enum 
values as a compile option.

Now I have something like this:
version (Parser) {
	enum Application = "parser";
}
version (Report) {
	enum Application = "report";
}

But would be nice to have posibility to add same value as a 
compile parametr, so I could have code like this:

enum Application = __traits(getParametrValue, 
"MY_APPLICATION_NAME");

and compile code with some args for eg.: 
-VMY_APPLICATION_NAME=parser