YES (VAR x1 x0 x y z) (RULES i2(f(x1,x0)) -> f(i2(x0),i2(x1)) i1(f(x1,x0)) -> f(i2(x0),i1(x1)) f(i1(x0),x1) -> f(i2(x0),x1) i2(i2(i2(x0))) -> i2(x0) i3(x0) -> f(i2(x0),a3()) i1(i2(i2(x0))) -> i1(x0) f(i2(x1),f(x1,x0)) -> x0 f(i2(i2(x0)),x1) -> f(x0,x1) i1(i1(x0)) -> i1(i2(x0)) f(x0,i1(a3())) -> i1(i2(x0)) i2(i1(x0)) -> i2(i2(x0)) f(x0,a2()) -> i2(i2(x0)) f(x,i1(x)) -> i1(a3()) f(x1,f(i2(x1),x0)) -> x0 i1(a2()) -> i1(a3()) a1() -> i1(a3()) i2(a2()) -> a2() i2(a3()) -> a2() f(x,i2(x)) -> a2() f(a3(),y) -> y f(a2(),y) -> y f(f(x,y),z) -> f(x,f(y,z)) ) (COMMENT Termination is shown by EKBO with interpretations on natural numbers f_A(x1,x2) = x1 + x2 + 2 a1_A = 10 a2_A = 0 a3_A = 0 i1_A(x1) = x1 + 1 i2_A(x1) = x1 i3_A(x1) = x1 + 5 a1#_A = 0 a2#_A = 0 a3#_A = 0 i1#_A(x1) = x1 weights w0 = 1 w(f) = 2 w(a1) = 3 w(a2) = 1 w(a3) = 1 w(i1) = 1 w(i2) = 0 w(i3) = 5 and precedence: i2 > a1 > i1 > i3 > f > a2 > a3 )