0.00/0.01 YES 0.00/0.01 We consider the system theBenchmark. 0.00/0.01 0.00/0.01 Alphabet: 0.00/0.01 0.00/0.01 0 : [] --> a 0.00/0.01 add : [] --> a -> a -> a 0.00/0.01 curry : [a -> a -> a] --> a -> a -> a 0.00/0.01 plus : [] --> a -> a -> a 0.00/0.01 s : [a] --> a 0.00/0.01 0.00/0.01 Rules: 0.00/0.01 0.00/0.01 plus 0 x => x 0.00/0.01 plus s(x) y => s(plus x y) 0.00/0.01 curry(f) x y => f x y 0.00/0.01 add => curry(plus) 0.00/0.01 0.00/0.01 This AFS is converted to an AFSM simply by replacing all free variables by meta-variables (with arity 0). 0.00/0.01 0.00/0.01 Symbol curry is an encoding for application that is only used in innocuous ways. We can simplify the program (without losing non-termination) by removing it. This gives: 0.00/0.01 0.00/0.01 Alphabet: 0.00/0.01 0.00/0.01 0 : [] --> a 0.00/0.01 add : [] --> a -> a -> a 0.00/0.01 plus : [] --> a -> a -> a 0.00/0.01 s : [a] --> a 0.00/0.01 0.00/0.01 Rules: 0.00/0.01 0.00/0.01 plus 0 X => X 0.00/0.01 plus s(X) Y => s(plus X Y) 0.00/0.01 add => plus 0.00/0.01 0.00/0.01 We use rule removal, following [Kop12, Theorem 2.23]. 0.00/0.01 0.00/0.01 This gives the following requirements (possibly using Theorems 2.25 and 2.26 in [Kop12]): 0.00/0.01 0.00/0.01 plus 0 X >? X 0.00/0.01 plus s(X) Y >? s(plus X Y) 0.00/0.01 add >? plus 0.00/0.01 0.00/0.01 We orient these requirements with a polynomial interpretation in the natural numbers. 0.00/0.01 0.00/0.01 The following interpretation satisfies the requirements: 0.00/0.01 0.00/0.01 0 = 3 0.00/0.01 add = \y0y1.3 + 3y0 + 3y1 0.00/0.01 plus = \y0y1.3y0 + 3y1 0.00/0.01 s = \y0.3 + y0 0.00/0.01 0.00/0.01 Using this interpretation, the requirements translate to: 0.00/0.01 0.00/0.01 [[plus 0 _x0]] = 12 + 4x0 > x0 = [[_x0]] 0.00/0.01 [[plus s(_x0) _x1]] = 12 + 4x0 + 4x1 > 3 + 4x0 + 4x1 = [[s(plus _x0 _x1)]] 0.00/0.01 [[add]] = \y0y1.3 + 3y0 + 3y1 > \y0y1.3y0 + 3y1 = [[plus]] 0.00/0.01 0.00/0.01 We can thus remove the following rules: 0.00/0.01 0.00/0.01 plus 0 X => X 0.00/0.01 plus s(X) Y => s(plus X Y) 0.00/0.01 add => plus 0.00/0.01 0.00/0.01 All rules were succesfully removed. Thus, termination of the original system has been reduced to termination of the beta-rule, which is well-known to hold. 0.00/0.01 0.00/0.01 0.00/0.01 +++ Citations +++ 0.00/0.01 0.00/0.01 [Kop12] C. Kop. Higher Order Termination. PhD Thesis, 2012. 0.00/0.01 EOF