On Wednesday, 9 January 2013 at 15:10:47 UTC, bearophile wrote:
eles:
void make_a_equal_to_b(??a,!!b); //I give you "b", give me "a"
A saner syntax is just to use the same in/out/inout keywords at
the call point, This is essentially what C# does (with one
exception for COM):
make_a_equal_to_b(ref a, in b)
This feature was discussed several times in past for D. The
advantage is more readability for the code and less surprises.
The disadvantages are more typing, some code breakage of D2
code (because even if at the beginning it's a warning, and
later a deprecation, you will eventually need to enforce it
with an error).
The same thing happens every time this is discussed: some people
insist "ref" and "out" should be REQUIRED or else it should not
be ALLOWED. Others don't want to break backward compatibility so
they insist it can't be required. There is no common ground so it
never gets to the "allowed" stage.
In C++ I actually use call site ref for & params even with no
checking at all:
#define IN
#define OUT
in fact these are defined in a Microsoft header. I find them
useful for documentation.
Again, my proposal is that the compiler should allow ref/out and
not warn when it is missing; if users want a warning/error for
missing ref/out, they can ask for it per-module with a pragma (or
something).
One more small D-specific problem is what to do if the first
argument is a ref and you want to use UCFS.
In the past I suggested allowing implicit ref for structs (but
probably not for classes) with UFCS, because the "this" parameter
of a member function of a struct is passed by ref already.
