(VAR y x z)
(RULES
   +(0,y) -> y
   +(s(0),y) -> s(y)
   +(s(s(x)),y) -> s(s(+(y,x)))
   +(x,+(y,z)) -> +(+(z,y),x)
)
(COMMENT from a collection of Aoto/Toyama, FSCD 2016)