On 09/15/2018 04:29 PM, Jonathan M Davis wrote:
Adding any sort of Concepts feature to D
would be very much at odds with DbI.
I'm not very familiar with C++'s attempted approaches to concepts, so
maybe we're thinking of two different things by "concepts", but I don't
see why it would be at odds with DbI. If anything, they would seem to
compliment each other well, each one filling in where the other hits its
limit. Even just a simple example:
void foo(ForwardRange r1, InputRange r2)
if(hasLength!r1)
{...}
Andrei is right that a no-DbI version of that would suck: Hierarchies
are no good for a series of orthogonal options. But at the same time,
the equivalent current-D code would comparatively be a mess, too.
Although...and maybe I'm just typing out of my &%@ here, maybe some kind
of templated concept:
void foo(ForwardRange!WithLength r1, InputRange r2)
{...}
Overall though, I don't think that there's really any disagreement that it
would be very desirable to get the compiler to provide better information
about which parts of a template constraint are true and which are false. The
problem is really that someone needs to come up with a scheme to do so that
will work reasonably well and then implement it, and no on has done that
yet.
Agreed, but let's be realistic, this *is* D: How many years has it been
since assertPred was rejected in favor of the improved-assert-messages
vaporware? It's hard to have much faith in such a thing happening here
either. (Not that I'm under any illusion that concept-like stuff would
be any more likely.)
Though, I'd be glad to be proven wrong either way.
-- Danny Downer
