Transients or scoped immutability

[bearophile]

Don:

> Just use a delegate literal (with a fix to 5081).

So I think you are suggesting a solution to my original problem similar to:


void foo(char[] data) {
    const count_bar = pure {
        int[256] count;
        foreach (char c; data)
            count[c]++;
        int x = ...
        auto bar = map!(...)(...x...);
        return tuple(count, bar);
    }();

    const count = count_bar[0];
    const bar = count_bar[1];
    // Here x is not visible.
    // Here count and bar are visible but read-only.
}
void main() {
    foo("this is a string");
}


This is less nice looking than possible alternatives, but it's not terrible, expecially if the tuple unpacking syntax sugar gets added to D:
(How do you create pure delegates? A syntax like this doesn't work: const x= pure {return 0;})


void foo(char[] data) {
    const (count, bar) = pure {
        int[256] count;
        foreach (char c; data)
            count[c]++;
        int x = ...
        auto bar = map!(...)(...x...);
        return tuple(count, bar);
    }();

    // Here x is not visible.
    // Here count and bar are visible but read-only.
}
void main() {
    foo("this is a string");
}

Bye,
bearophile