YES exiting with thread! (VAR x y z ) (RULES f(f(x,y),z) -> f(x,f(y,z)) f(x,i(x)) -> e f(x,e) -> x f(a,f(a,f(a,a))) -> e f(b,b) -> e i(e) -> e f(e,x) -> x f(i(x),x) -> e f(x,f(i(x),z)) -> z f(b,f(b,z)) -> z i(b) -> b i(i(y)) -> y f(a,f(a,f(a,f(a,z)))) -> z f(i(x),f(x,z)) -> z i(a) -> f(a,f(a,a)) f(b,a) -> f(a,f(a,f(a,b))) f(b,f(a,z)) -> f(a,f(a,f(a,f(b,z)))) i(f(y,x)) -> f(i(x),i(y)) )