[dmd-internals] Keywords starting with __ and version identifiers

[Robert Clipsham]

This could be done in the runtime/phobos - is(typeof()) is standard D, so
something like:

enum supportsTraits = is(typeof(__traits(compiles, {})));

Could be used.

On another note, dmd, gdc and ldc all use DMDFE, and all support the __
keywords mentioned. SDC will also support them... They're so ubiquitous in
D code currently they can't *not* be supported.

On 29 December 2011 11:56, Alex <xtzgzorex at gmail.com> wrote:

> Hi,
>
> DMD currently has two keywords (AFAIK) starting with double
> underscore: __traits and __gshared, and additionally, __ctfe (though
> it isn't really a keyword)
>
> From what I can understand, they are implementation-dependent, and
> thus not necessarily available in all compilers. This is reasonable
> enough, but presently, there is no universal way to detect whether the
> keywords are available. That means that any code that uses them simply
> relies on the compiler having them, period. I don't think this is
> optimal, nor is it good language design IMHO.
>
> I think we need to have version identifiers that indicate whether they
> are available, e.g.:
>
> version (__traits)
> {
>    enum compiles = __traits(compiles, { ... });
> }
> else
> {
>    // Fall back to some other mechanism, perhaps some feature
> provided by a non-DMD compiler...
> }
>
> Thoughts on this?
>
> Regards,
> Alex
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>



-- 
Robert
http://octarineparrot.com/
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