On Friday, 2 May 2014 at 08:17:09 UTC, Mark Isaacson wrote:
I'm in the process of learning/practicing D and I noticed
something that seems peculiar coming from a C++ background:
If I compile and run:
void fun(const ref int x) {
//Stuff
}
unittest {
fun(5); //Error! Does not compile
}
I get the specified error in my unit test. I understand that
the cause is that I've attempted to bind ref to an r-value,
what's curious is that in C++, the compiler realizes that this
is a non-issue because of 'const' and just 'makes it work'. Is
there a rationale behind why D does not do this? Is there a way
to write 'fun' such that it avoids copies but still pledges
const-correctness while also allowing r-values to be passed in?
There is `auto ref`, but it only works for templates and is
somewhat different:
void fun()(auto ref const int x) {
// Stuff
}
unittest {
fun(5); // pass by value
int a = 5;
fun(a); // pass by ref
}
It generates two functions, with and without ref respectively.
Allowing rvalues to bind to ref (not only const) has been
discussed on several occasions, but I don't remember the outcome.
Here is one discussion:
http://forum.dlang.org/thread/ntsyfhesnywfxvzbe...@forum.dlang.org
