In many cases, when it is needed to check if a container not empty, "size()" or "empty()" functions are used:

if (vect.size() != 0) {

    // vector is not empty

}

if (!vect.empty()) {

    // vector is not empty

}

It seems that both variants are not expressive enough, so an explicit function may be required, like:

if (vect.not_empty()) {

    // vector is not empty

}

In this message I would like to suggest to use of a bool casting operator as the most clean form of this function:

if (vect) {

  // vector is not empty

}

The proposal seems to be backward compatible because until now there was no bool casting operator defined in standard container classes.

(and it is not possible to define a global one).