Re: [boost] Re: New New Callbacks Uploaded

From: Peter Dimov (pdimov_at_[hidden])
Date: 2000-11-23 11:55:27

From: "Kevlin Henney" <kevlin_at_[hidden]>

> >The counted callback more closely mirrors a function pointer, in the case
> >where the function has state (static variables.)
>
> Not sure I agree that it does quite make this case. I think built-in
> semantics are surprisingly neutral on the topic.

Actually the built-in semantics aren't exactly duplicated by the counted
callback, also:

int f()
{
    static int i = 0;
    return ++i;
}

int (*g)() = f;
int (*h)() = g;

f(); // 1
g(); // 2
h(); // 3

--
class F
{
public:
    F(int j): i(j) {}
    int operator()() { return ++i; }
private:
    int i;
};
{
    F f;
    counted_callback<int> g(f);
    counted_callback<int> h(g);
    f(); // 1
    g(); // 1
    h(); // 2
}
{
    F f;
    cloning_callback<int> g(f);
    cloning_callback<int> h(g);
    f(); // 1
    g(); // 1
    h(); // 1
}
--
Peter Dimov
Multi Media Ltd.