On Monday, 12 May 2014 at 04:22:21 UTC, Marco Leise wrote:
On the positive side the talk about Rust, in particular how
reference counted pointers decay to borrowed pointers made me
think the same could be done for our "scope" args. A reference
counted slice with 3 machine words could decay to a 2 machine
word "scoped" slice. Most of my code at least just works on the
slices and doesn't keep a reference to them. A counter example
is when you have something like an XML parser - a use case
that D traditionally (see Tango) excelled in. The GC
environment and slices make it possible to replace string
copies with cheap slices into the original XML string.
Rust also has a solution for this: They have lifetime
annotations. D's scope could be extended to support something
similar:
scope(input) string getSlice(scope string input);
or with methods:
struct Xml {
scope(this) string getSlice();
}
scope(symbol) means, "this value references/aliases (parts of)
the value referred to by <symbol>". The compiler can then make
sure it is never assigned to variables with longer lifetimes than
<symbol>.
