const debacle

[Walter Bright]

Janice Caron wrote:
> It /doesn't/ modify the input,

By returning the input as a modifiable aggregate, it breaks its promise 
not to modify it. The cast to remove const-ness is where the problem is. 
Consider again:

    T[] f(const T[]);
    void g(T[]);

    ...

    T[] t;
    g(f(t));
    ... (*) ...

Let's say g() modifies its argument. Then, at point (*), t has changed, 
even though t was passed to a function that promised not to mutate it. 
This is fundamentally a broken program.