Walter Bright wrote:
Rainer Deyke wrote:
Andrei Alexandrescu wrote:
Eiffel offers the "old" keyword that refers to the old object in a
postcondition. But it seems quite wasteful to clone the object just to
have a contract look at a little portion of the old object.
You don't need to clone the whole object. You just need to cache the
properties that are used with 'old'.
That's a good idea.
Should work, but it has more than a few subtleties. Consider:
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.
Andrei
