current_frame() takes in redundant argument length

[rishflab]

   pub fn current_frame(&self, strip: Range<usize>, length: f32, elapsed: f32) -> u8 {
        let dt = elapsed % length;
        let mut frame = 0;
        for f in self.0[strip].iter().rev() {
            if dt > f.time {
                frame = f.index;
                break;
            }
        }
        frame
    }

length is the last value in strip. does not need to be passed as an arg. extract length from strip.last or something