Specifying C++ symbols in C++ namespaces
Michel Fortin
michel.fortin at michelf.ca
Sat Apr 5 14:55:11 PDT 2014
On 2014-04-05 20:47:32 +0000, Walter Bright <newshound2 at digitalmars.com> said:
> On 4/2/2014 3:07 PM, Walter Bright wrote:
>> One downside of this proposal is that if we ever (perish the thought!)
>> attempted
>> to interface to C++ templates, this design would preclude that.
>
> Yes, this seems to be a fatal flaw. Another design that has evolved
> from these discussions and my discussions with Andrei on it:
>
> extern (C++, namespace = A.B) { void foo(); void bar(); }
> extern (C++, namespace = C) void foo();
>
> bar(); // works
> A.B.bar(); // works
> foo(); // error: ambiguous
> C.foo(); // works
>
> alias C.foo foo;
> foo(); // works, calling C.foo()
>
> I really think the namespace semantics should be attached to the
> extern(C++) rather than be a separate pragma. Having the namespace=
> thing means that namespace isn't a keyword, and provides a general
> mechanism where we can add language specific information as necessary.
I like this idea. But... should this potentially useful thing really be
restricted to extern C++ things? I've seen at least one attempt to
create a namespace using what D currently offers [1], and frankly
something like the above would make much more sense than a class no one
can instantiate.
[1]: http://dlang.org/phobos/std_datetime.html#.Clock
Here's a suggestion:
@namespace A.B { // can create two levels at once, yeah!
void foo();
void bar();
}
@namespace C {
void foo();
}
Make those C++ declarations, it does not look too foreign anymore:
extern (C++) @namespace A.B {
void foo();
void bar();
}
extern (C++) @namespace C {
void foo();
}
--
Michel Fortin
michel.fortin at michelf.ca
http://michelf.ca
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