probably something like that :

you can use the modulus (%~) to make a basic wrapping function. folding is more difficult though. you have to do a fair bit of screwing around with it if you want it to fold down then up then down then up within the respective + and - ranges like that picture shows. years ago i did it like this: first, you should notice that when you amp the wave (say from a peek of 1 to 3), and then modulus it, every even numbered multiple of 1, it should be subtracting the modulus result of the wave from 1, and every odd numbered time it should just be wrapping around. (this would create the up, down, up down pattern in the picture. you have to use a lot of logic objects and all that stuff.

im sorry i cant be of more direct help, i made a patch that did this really well a few years ago, (it would fold/wrap around the whole range of 1 to -1, or just 1 to 0, and mirror it in the 0 to -1 range respectively), but the hard drive is corrupted.