function to increment/decrement and cycle through a range

Cycle through values in C++/Arduino

Increment or decrement by an integer value, (normally +1 or -1)  but cycle between min and max constraints. Test code at gitHub

        EX: dec by -1    4  3  2  1    4  3  2  1
            inc by +2   -4 -2  0  2   -4 -2  0  2

int16_t cycleIncDec(int16_t x, int16_t dir, int16_t xmin, int16_t xmax) {

    // inc/dec with constrained range

    // supplied xmax must be greater than xmin

    x += dir;

    if      (x > xmax) x = xmin;

    else if (x < xmin) x = xmax;

    return x;

}