C++:

#include <cassert>
#include <string>
#include <iostream>

using namespace std;

struct lim {
    const double min = -10, max = 10;
    double val;
    lim(double v) {
        assert(v >= min && v <= max);
        val = v;
    }
    lim& operator=(double v) {
        assert(v >= min && v <= max);
        val = v;
    }
    operator double() const {
        return val;
    }
};

struct point {
    lim x,y;
    point(double _x, double _y)
        : x(_x), y(_y) { }
};
ostream& operator<<(ostream& s, const point& p) {
    s << "[" << + p.x << "," << p.y << "]";
    return s;
}

int
main() {
    point p(5,3);
    cout << p << endl;
    p.y = 17.3;
    cout << p << endl;
}