Tell me, please, is it possible to set an arbitrary condition conditional compilation at the command prompt, type DUSE_MYLIB12 and in the code as:

version(USE_MYLIB12) {
       .....
}

And I didn't like Any DeclarationBlock or Statement that is not compiled in still must be syntactically correct:
http://dlang.org/version.html

It may be that using an optional library code is correct, and without it not?

On Wednesday, 11 February 2015 at 11:26:20 UTC, Dennis Ritchie wrote:
> Tell me, please, is it possible to set an arbitrary condition conditional compilation at the command prompt, type DUSE_MYLIB12 and in the code as:
>
> version(USE_MYLIB12) {
>        .....
> }

Specify -version=USE_MYLIB12 on the command line.

> And I didn't like Any DeclarationBlock or Statement that is not compiled in still must be syntactically correct:
> http://dlang.org/version.html
>
> It may be that using an optional library code is correct, and without it not?

No, that's not possible. Syntactically correct != semantically correct. It just means that the syntax rules of the language are respected, e.g. parens must be correctly nested (no [} or something like that). Since D libraries can't affect the syntax of the language, no code can be syntactically correct only in that library's presence.

Thanks.