Why version() ?

[Walter Bright]

Denis Koroskin wrote:
> Does it look any better? No way!

Of course doing it that way doesn't look any better, because it still 
just replicates the C preprocessor style of doing it.

A far better solution is to create a series of modules:

gcnetbsd.d
gchurd.d
gcsunos5.d
...

and inside each one put the specifics for that particular system. The 
huge advantage of this is that if I want to create a BrightBSD operating 
system, I just have to write a:

gcbrightbsd.d

rather than trying to carefully fold it into that conditional 
compilation mess without inadvertently breaking other platform support. 
(And I cannot even tell if I broke the SunOS5 platform support or not, 
because I don't have a SunOS5 platform to test it on.)


> The story is not about different functionality on different platforms 
> but rather about a common code which is 98% the same on all the 
> platforms and is different in *small* details.
> For example, I'd like to 
> make my library D1 and D2 compatible. Do you suggest me to maintain 2 
> different libraries? This is ridiculous, and that's why there is no 
> Tango2 release yet - there is *no* point in supporting such a large 
> library as Tango (or DWT) for two language versions without a sane 
> versioning mechanism.

There are two very different things going on here. One is accounting for 
differences in the *language*, the other is about generating different 
builds based on language independent different desired features and 
platform characteristics.

I agree that version is not a solution to the D1/D2 language difference 
problem, and furthermore contend it cannot be coerced into being one. 
The only real solution, other than maintaining separate source files, is 
to use a text macro preprocessor.

(Sadly, the C preprocessor cannot be used, because it is a tokenizing 
textual preprocessor, and C preprocessor tokens are different from D 
tokens.)