version(number) is completely useless

[Andrey Zherikov]

On Wednesday, 20 July 2022 at 01:34:00 UTC, Steven Schveighoffer 
wrote:
> On 7/19/22 9:22 PM, Andrey Zherikov wrote:
>> I actually have a question since this topic is brought up:
>> What is conceptual difference between `version(FOO)` and 
>> `static if(FOO)`? I see `version` is a very limited comparing 
>> to `static if` - the former checks for "boolean" result 
>> (whether an ID is defined) while the latter evaluates 
>> condition expression.
>
> version is specifically a replacement for #defines as in C. 
> They are specified mostly on the command line.

It's not a full replacement because it doesn't support 
`-DSOME_DEFINE=5` or `-DANOTHER_DEFINE="some string"`.

One of the features which I really miss in D is inability to do 
these things. This is very largely used in software development 
for setting compile-time constants from command line. D doesn't 
support this out of the box (I have to dump a `.d` file with set 
of `enums` and then include it into the build).

> But also, a version cannot be detected from an imported file -- 
> every module starts with the compilation versions, and that's 
> it.
>
> Walter was very averse to the mess that is C preprocessor 
> defines, and wanted something more hygienic.

I'm totally for simple and clean solution here but whatever D 
offers right now is half-baked IMHO.

> The thing I miss the most for versions is a `version1 or 
> version2` mechanism. I doubt we will ever convince Walter this 
> is a good idea.

I don't think that `version1 or version2` is any different than 
allowing complete conditional expression.

> But in any case, we have the numeric versions, which are 100% 
> useless (because, as you say, they are not scoped to any 
> dependencies), it would make sense to at least make that 
> feature useful.

I don't see how raw numbers can be useful. Could you clarify your 
idea?