On 12/19/18 2:58 PM, Neia Neutuladh wrote:
On Wed, 19 Dec 2018 17:28:01 +0000, Vijay Nayar wrote:
Could you please elaborate a little bit more on this? In the linked
program, I had expected that "ref" would return a reference to "a" that
would behave similar to a pointer.
They work like pointers that automatically dereference when assigning to
the base type.
Only three things in D can be ref:
* A function parameter
* A function return value
* A foreach variable (since that's either going to be a function return
value, a function parameter, or a pointer, depending on what you're
iterating over)
So when the compiler sees something like:
ref int foo();
auto a = foo();
It sees that the type of 'a' has to be the same as the return type of
'foo'. Except that's not possible, so it uses the nearest equivalent type:
int.
I would say it a little bit differently -- the return *type* of foo is
int. In D, ref is not part of the type at all.
For example, even when it *could* use ref, it doesn't:
int x;
ref int foo() { return x; }
void bar(Args...)(Args args)
{
pragma(msg, __traits(isRef, args[0]));
}
bar(foo()); // outputs false at compile time
The storage class is completely separate from the type. Which is
different from C++, where it's like a storage class but is really a type
constructor, hence Walter's post.
-Steve
