On Monday, 14 September 2020 at 18:58:44 UTC, 60rntogo wrote:
On Monday, 14 September 2020 at 17:11:59 UTC, k2aj wrote:
AFAIK the only way to have default ref arguments is to use a
global variable:
---
extern(C++) struct Foo
{
int x;
}
immutable foo1 = Foo(1);
extern(C++) void fun(const ref Foo foo = foo1);
---
Thanks. This appears to work, but feels like a hack. I can live
with that, but I'm still wondering if there is a more idiomatic
way of solving the problem.
D doesn't let rvalues bind to const ref (well, `in` will do that,
but it's D-only).
What was described as "global variable", is more of a "manifest
constant lvalue".
A (static) immutable variable with an initializer will always be
CTFE-d and available at compile time, so in this case it is
*exactly* what you need.
Also note that a default parameter doesn't affect the mangling /
ABI, because it works exclusively on the caller side. Thus, you
could just remove the default argument and your `extern(C++)`
binding would work just fine. But if you want to provide the same
API, `[static] immutable` + initializer is the way to go.
