Proposal for scoped const contracts

[Janice Caron]

On 24/03/2008, Walter Bright <newshound1 at digitalmars.com> wrote:
>  For me, the question is is solving these issues a large enough problem
>  that justifies adding a rather confusing new variation on const?

We can trade! :-)

We could drop "in" as a function parameter attribute. I find the
difference between "in" and "const" to be somewhat unfathomable.
Removing "in" would simplify the const system, with, as far as I can
see, no real loss.

See - you can add variations with one hand, and take them away with
the other! :-)

However, I can see a problem with the "return" syntax, exemplified by
the following example.

    const(char)[] g = "hello"; // global variable

    char[] f(return char[] s)
    {
        return g;
    }

    char[] s;
    s = f(s);
    s[0] = 'x';

It's not just the constancy you have to worry about. You also have to
prove that you are actually returning what you claim you're returning.
As in, the actual variable. That's why I earlier suggested

    sliceof(t) foo(const(T) t)

...although "sliceof" is clearly the wrong word, since [] is not
defined for all types.