OpenBSD port of dmd?

[Sean Kelly]

In truth it would be

else version (Posix)

Anyway, which isn't the bare else Walter was advising against. 

On Mar 17, 2012, at 5:10 PM, Alix Pexton <alix.DOT.pexton at gmail.DOT.com> wrote:

> On 17/03/2012 16:43, Andrei Alexandrescu wrote:
>> On 3/17/12 9:10 AM, Sean Kelly wrote:
>>> Pretty much. I'd expect to see:
>>> 
>>> version (linux) {
>>> // optimized impl
>>> } else version (OSX) {
>>> version = UseDefault;
>>> } else {
>>> static assert(false, "unknown platform");
>>> }
>>> version (UseDefault) {
>>> ...
>>> }
>> 
>> Taking this to its logical conclusion means that _all_ code that is
>> currently unguarded must be guarded by version (UseDefault).
>> 
>> Andrei
>> 
>> 
> 
> Firstly, I don't think the name "UseDefault" was well chosen for this example. I don't think its meant to be a catch all for every occasion when version statements are used. Perhaps "NoFeatureXyzIntrinsic" would be clearer.
> 
> Secondly, if every line of D code is potentially platform-specific and/or inherently inefficient unless optimised with some case specific intrinsic, then there must be some glaring problems with the abstractions that the language provides.
> 
> I will also reiterate that I believe that there are 2 different cases being considered together here.
> _Compatibility_, where asserting in the else of a version statement is the best course of action.
> _Opportunistic-Optimisation_, where providing a default case in the else as a fall back is quite sensible.
> 
> The scenario which applies can often be easily deduced, it is my experience that optimisations are "versioned-in" while incompatibilities are "versioned-out".
> i.e. Adding a platform specific optimisation is "versioning-in", and the prior platform agnostic code becomes the default. Proofing a platform specific module is "versioning-out" removing inapplicable code and leaving a note for the maintainer that other platforms will require their own implementation.
> 
> In the cases where the programmer does not have enough knowledge to know which scenario applies (perhaps not knowing if a particular intrinsic has compatible implementations across all platforms), I find it hard to find any argument in favour of providing a default action that may have unknown effects on another system.
> 
> A...