Why version() ?

[Walter Bright]

Nick Sabalausky wrote:
> This strikes me as throwing away the baby with the bathwater. If your code 
> starts degenerating towards a versioning rat's nest, then the solution is to 
> take a moment and refactor it into a larger granularity, not to throw away 
> features that are useful in moderation.

True, but that never, ever happens. It's always "I can get my few 
additions to this rat's nest in and just get it working, and worry about 
proper abstraction later."

>> 1. Why not version(!feature) ?
>>
>> Because cognitive studies show that people just don't see the negation.
> 
> Isn't that moreso a case against the ! operator in general? I don't see how 
> "if(!blah)" is any less susceptible to overlooking the ! than 
> "version(!blah)".

Yes, you're right, it's both a minor and an inconsistent point, despite 
it being right <g>.


>> Secondly, when you see things like:
>>
>>     version (!linux) { ... }
>>
>> they're almost always wrong. Versions should be positive things, because a 
>> version is something that is being build - one doesn't craft a makefile to 
>> build a notLinux.
> 
> True, we don't build to a NotLinux, but we do however build to "everything 
> except platform X".

We do, and they're always wrong. I always find when doing that and 
porting to another machine that those #if !linux must be reengineered. I 
have switched entirely over to:

#if Windows
    ...
#elif linux
    ...
#elif __APPLE__
    ...
#else
    assert(0); // fix when adding a new platform
#endif

because otherwise I *miss* sections that need updating when porting to a 
new platform, and have a bug that needs tracking down.

The point is, when writing portable code, especially code that will be 
ported by others, you have *no idea* what platforms will fall into the 
"notLinux" section and what peculiarities those platforms might have. It 
works much better to have the compiler ding me when it encounters 
platform specific code that doesn't have a section for the platform I'm 
compiling for.

> And I don't see how a "LinuxOrMac" (or worse yet, a 
> "LinuxOr_MacAndSomeOtherCharacteristic_") is any more or less of a realistic 
> platform than a "NotLinux".

Based on my experience porting code, LinuxOrMac is a far better solution 
(i.e. faster to code, faster to port, fewer bugs) than notWindows.


> Also, you didn't respond to the concerns about typos in a version 
> identifier. Can we assume you agree that's a problem? 

It's a problem without a solution unless you propose adding some sort of 
declaration syntax for all the version identifiers.