Rainer Deyke wrote:
Andrei Alexandrescu wrote:
class A {
int fun() { ... }
int gun(int) { ... }
int foo()
in {
}
out(result) {
if (old.fun())
assert(old.gun(5));
else
assert(old.fun() + old.gun(6));
foreach (i; 1 .. old.fun())
assert(gun(i * i));
}
...
}
Now please tell what's cached and in what order.
The following are cached, in this order:
fun()
gun(5)
gun(6)
Old values are calculated in the order in which they appear in the
function, but only once each.
Rats, I meant assert(old.gun(i * i)). That's what compounds the
difficulty of the example.
However, I strongly prefer the following syntax:
class A {
int fun() { ... }
int gun(int) { ... }
int foo()
in {
}
out(result) {
if (old(fun()))
assert(old(gun(5)));
else
assert(old(fun()) + old(gun(6)));
foreach (i; 1 .. old(fun()))
assert(gun(i * i));
}
...
}
This lets you distinguish between the following cases:
old(f().g())
old(f()).g()
It also lets you cache non-members:
old(arg);
old(global_var);
For example:
void increment_global_counter() out {
global_counter = old(global_counter) + 1;
}
I honestly believe the whole "old" thing can't be made to work. Shall we
move on to other possibilities instead of expending every effort on
making this bear dance?
Andrei
