YES (VAR x0 x1 x y) (RULES eq(x0,s(x1)) -> eq(p(x0),x1) eq(s(x0),x1) -> eq(x0,p(x1)) eq(p(x),p(y)) -> eq(x,y) eq(p(x),x) -> false() eq(x,p(x)) -> false() eq(x,x) -> true() p(s(x)) -> x ) (COMMENT Termination is shown by ELPO with interpretations on natural numbers p_A(x1) = x1 + 1 s_A(x1) = x1 + 2 eq_A(x1,x2) = x1 + x2 true_A = 0 false_A = 1 eq#_A(x1,x2) = x1 + x2 true#_A = 0 false#_A = 0 and precedence: eq > p > s > true > false )