Function pingpong 

pub fn pingpong(value: f64, length: f64) -> f64

Wraps value between 0 and the length. If the limit is reached, the next value the function returns is decreased to the 0 side or increased to the length side (like a triangle wave). If length is less than zero, it becomes positive.

pingpong(-3.0, 3.0) # Returns 3.0
pingpong(-2.0, 3.0) # Returns 2.0
pingpong(-1.0, 3.0) # Returns 1.0
pingpong(0.0, 3.0)  # Returns 0.0
pingpong(1.0, 3.0)  # Returns 1.0
pingpong(2.0, 3.0)  # Returns 2.0
pingpong(3.0, 3.0)  # Returns 3.0
pingpong(4.0, 3.0)  # Returns 2.0
pingpong(5.0, 3.0)  # Returns 1.0
pingpong(6.0, 3.0)  # Returns 0.0