On Tuesday, 20 December 2016 at 14:47:28 UTC, Walter Bright wrote:
On 12/20/2016 5:47 AM, Ilya Yaroshenko wrote:
One good thing for safety and CTFE is allow multiple return
value. In
combination with `auto ref` it is _very_ powerful:
----
auto ref front()
{
// Returns 2 values, each value is returned by reference if
possible
return (a.front, b.front);
}
----
http://dlang.org/phobos/std_typecons.html#.tuple
auto ref front() {
return tuple(a.front, b.front);
}
Tuples can not work with auto ref. This is a reason for this
thread.
Proof:
-----
import std.typecons: tuple;
int[] a = [1,2,3];
int[] b = [1,2,3];
auto ref front() {
import std.range: front;
return tuple(a.front, b.front);
}
void main()
{
front()[0] = 1000;
import std.stdio;
writeln(front()[0]);
}
-----
Output: 1
-----
As you can see the output should be 1000, but it is 1.
It can be solved with pointers, and Mir will have their own
tuples which use pointers. But it is not good because:
1. Pointers are not CTFE-able.
2. Pointers are not safe.
