On 2013-11-20 23:35:00 +0000, Meta said:
On Wednesday, 20 November 2013 at 23:27:38 UTC, Shammah Chancellor wrote:
I just watched this talk from the goto conference by Walter Bright
(https://www.youtube.com/watch?v=cQkBOCo8UrE) and he makes reference to
"concepts." However, they look almost identical to Protocols in
Smalltalk -- something which I would very much like to see in D.
It basically works much like an interface, but instead of declaring it,
you check the type to see if it defines the appropriate methods.
In fact -- I believe this could be implemented today with __traits and
static foreach to simply check to see if a type conforms to a protocol
at compile time.
implementsProtocol!( R, InputRange!(int) );
where InputRange!() could just be a templated interface.
Having this in phobos would be really helpful! If there is interest
in this, I'll write a template up and submit it to phobos.
-Shammah
Something that's almost exactly what you're looking for:
http://dlang.org/phobos/std_typecons.html#.wrap
http://dlang.org/phobos/std_typecons.html#.unwrap
Also, note that this is pretty much how D templates work. The
difference between concepts and protocols is that concepts work at
compile time, while protocols work at runtime. Interfaces, a la Java
are a hybrid. That's really just an implementation detail, though. None
of these terms are all that well defined across all or even most
programming languages.
Wrap does something similar, but more (since I don't want a wrapper).
I just want to check it at compile time. Something like this should
be standard instead of isInputRange!() and the plethora of "concept
checkers" in various libraries. It seems like we're developing a web
of these concept-checkers and it's hard to see what I should implement
to be an "InputRange" from the documentation. If there was a standard
interface for it, and a library-defined checker, it would be more
consistent across the codebase and easier to see what specifically
needs to be implemented.
