D alternative for C/C++ -Dfoo=42

[Dejan Lekic]

On Tuesday, 25 February 2014 at 12:45:06 UTC, Cherry wrote:
> Hello
>
> I want to define an enum int, but I want to make it possible to 
> set its value when I run dmd from the command line. Is it 
> possible in D?
>
> Regards
> Cherry

D offers version blocks: http://dlang.org/version.html#version

It would be great if D compiler had a way to substitute enums 
with given values. (This is a nice candidate for a DIP)

Imagine you have a code like this:

module myproggy;
import std.stdio;
enum foo = 5;
enum bar = "walter";

int main() {
   writeln(bar);
   return foo;
}

... and you call compiler like:
   dmd myproggy.d -Dfoo=42 -Dbar=hello

smart, new D compiler would replace enums (iff they exist in the 
source code) with the given arguments, so when you run myproggy, 
you get "walter" as output, and the exit code is 42.