On Thu, Nov 04, 2021 at 05:24:44PM +0000, Andrey Zherikov via Digitalmars-d-learn wrote:
> On Thursday, 4 November 2021 at 17:09:31 UTC, Steven Schveighoffer wrote:
> > D doesn't have any equivalent for this.
> 
> Is it possible to add this feature having `-C VERSION="1.2.3"` (`-D` is already used) to be equal to `enum VERSION="1.2.3"` in global namespace?
> 
> > The closest you can get is to turn on `version` identifiers.
> > 
> > There is also a quirky `-version=123` which is IMO, a completely useless feature.
> 
> I agree - this is useless. `-version myversion=123` would be much more useful.

Here's a hack that uses dmd's stdin feature to inject D code into a compile command:

	// main.d
	import __stdin : myversion;
	void main() {
		import std;
		writeln(myversion);
	}

Compile command:
	echo 'enum myversion = "1.2.3";' | dmd - -run main.d

Output:
	1.2.3

You can change the version number just by changing the echo command. And of course, it doesn't have to be a string, it can be any valid D type, and obviously you can declare more than one variable that can then be read by importing from __stdin.


T

-- 
Don't throw out the baby with the bathwater. Use your hands...

On 11/4/21 10:36 AM, H. S. Teoh wrote:

> 	import __stdin : myversion;

Where can we learn more of that magic? :)

Ali

On Thu, Nov 04, 2021 at 01:17:02PM -0700, Ali Çehreli via Digitalmars-d-learn wrote:
> On 11/4/21 10:36 AM, H. S. Teoh wrote:
> 
> > 	import __stdin : myversion;
> 
> Where can we learn more of that magic? :)
[...]

I kinda cheated, because I was the one who implemented dmd's stdin feature, so I knew that dmd implicitly creates a specially-named module to contain the code read from stdin.  I had actually forgotten what the name of this module was, but that was no problem since it was easily found by:

	echo 'pragma(msg, __MODULE__);' | dmd -c -

which revealed the module name to be `__stdin`.

Next, thanks to D's module system, is the realization that you could import this implicit module from somewhere else and pull symbols from it.  From there, the everything else followed. :-)


T

-- 
There is no gravity. The earth sucks.