Memory management trickery with arrays
/// the first particle in the linked list
    Particle* start=0;

/// the next free particle
Particle* last=0;

/// the end of the memory allocation
Particle* end=0;

void SetSize(unsigned int size) {

    // delete any previous data
    delete [] start;

    // allocate new particles
    last = start = new Particle[size];

    // set end
    end = start+size;
}

void AddOne() {

    // if we have no more memory left for any particles, ignore
    // the request to creat one.
    if (!IsFull()) {
        *last = Particle();
        ++last;
    }

}

void EraseOne(Particle* p) {

    if (!IsEmpty()) {
        *p = *(--last);
    }

}