Method add

plugins/prospector.cpp:106–121

        upper_z = copyme.upper_z;
    }
    float add(int z_level = invalid_z, float delta = 1.0)
    {
        count += delta;
        if(z_level != invalid_z)
        {
            if(lower_z == invalid_z || z_level < lower_z)
            {
                lower_z = z_level;
            }
            if(upper_z == invalid_z || z_level > upper_z)
            {
                upper_z = z_level;
            }
        }
        return count;
    }
    float count;
    int lower_z;
    int upper_z;