On Saturday, 2 February 2013 at 07:10:00 UTC, TommiT wrote:
On Saturday, 2 February 2013 at 03:50:49 UTC, Zach the Mystic
wrote:
[..]
Then, if we used your proposed nested structs to implement
properties, pretty weird things like this would become possible:
struct A
{
int _value;
struct B
{
int get() { return _value; }
alias this = get;
void opAssign(int v) { _value = v; }
}
B length;
}
void func(T)(ref A a, T oldLength)
{
a.length = 100;
// Trying to restore 'a' back to the old length:
a.length = oldLength;
}
void main()
{
A a;
a.length = 5;
func(a, a.length);
assert(a.length == 100);
}
This code is both wrong and has nothing whatever to do with the
current topic. Boiling down the template to its resulting
function, and imagining _value as the intended entity:
void func(ref A a, int oldLength)
{
a._value = 100;
a._value = oldLength;
}
A a;
a._value = 5;
func(a, a._value);
assert(a._value == 5); // 5, not 100
func takes an int. It's not a reference, it's a copy.
Let's assume you meant void func(ref A a, ref int oldLength) {}
instead. Well, if you pass a reference, set it, and then refer
it, you're going to get the set value back. I'm sorry, you can't
adjust a reference and then expect to get a phantom original copy
back. While I may have made a mistake, I simply see no connection
between this and the idea of properties as structs.
