YES (VAR x y) (RULES p(x) -> -(x,s(0())) -(x,0()) -> x -(s(x),s(y)) -> -(x,y) +(x,0()) -> x +(x,s(y)) -> s(+(x,y)) dfib(s(s(x))) -> +(dfib(s(x)),+(dfib(x),dfib(x))) dfib(s(0())) -> s(0()) dfib(0()) -> s(0()) fib(s(s(x))) -> +(fib(s(x)),fib(x)) fib(s(0())) -> s(0()) fib(0()) -> s(0()) ) (COMMENT Termination is shown by ELPO with interpretations on natural numbers fib_A(x1) = 0 0_A = 0 s_A(x1) = x1 +_A(x1,x2) = x1 dfib_A(x1) = 1 -_A(x1,x2) = x1 p_A(x1) = x1 0#_A = 0 +#_A(x1,x2) = x2 -#_A(x1,x2) = x2 p#_A(x1) = x1 and precedence: p > dfib > fib > + > s > - > 0 )