/export/starexec/sandbox2/solver/bin/starexec_run_FirstOrder /export/starexec/sandbox2/benchmark/theBenchmark.xml /export/starexec/sandbox2/output/output_files


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MAYBE
We consider the system theBenchmark.

We are asked to determine termination of the following first-order TRS.

  0 : [] --> o 
  false : [] --> o 
  gcd : [o * o] --> o 
  ge : [o * o] --> o 
  gt : [o * o] --> o 
  if : [o * o * o] --> o 
  if1 : [o * o * o] --> o 
  if2 : [o * o * o] --> o 
  minus : [o * o] --> o 
  s : [o] --> o 
  true : [] --> o 

  minus(s(X), Y) => if(gt(s(X), Y), X, Y) 
  if(true, X, Y) => s(minus(X, Y)) 
  if(false, X, Y) => 0 
  gcd(X, Y) => if1(ge(X, Y), X, Y) 
  if1(true, X, Y) => if2(gt(Y, 0), X, Y) 
  if1(false, X, Y) => gcd(Y, X) 
  if2(true, X, Y) => gcd(minus(X, Y), Y) 
  if2(false, X, Y) => X 
  gt(0, X) => false 
  gt(s(X), 0) => true 
  gt(s(X), s(Y)) => gt(X, Y) 
  ge(X, 0) => true 
  ge(0, s(X)) => false 
  ge(s(X), s(Y)) => ge(X, Y) 

As the system is orthogonal, it is terminating if it is innermost terminating by [Gra95].  Then, by [FuhGieParSchSwi11], it suffices to prove (innermost) termination of the typed system, with sort annotations chosen to respect the rules, as follows:

  0 : [] --> de 
  false : [] --> he 
  gcd : [de * de] --> de 
  ge : [de * de] --> he 
  gt : [de * de] --> he 
  if : [he * de * de] --> de 
  if1 : [he * de * de] --> de 
  if2 : [he * de * de] --> de 
  minus : [de * de] --> de 
  s : [de] --> de 
  true : [] --> he 


+++ Citations +++

[FuhGieParSchSwi11]  C. Fuhs, J. Giesl, M. Parting, P. Schneider-Kamp, and S. Swiderski.  Proving Termination by Dependency Pairs and Inductive Theorem Proving.  In volume 47(2) of Journal of Automated Reasoning.  133--160, 2011.
[Gra95]  B. Gramlich.  Abstract Relations Between Restricted Termination and Confluence Properties of Rewrite Systems.  In volume 24(1-2) of Fundamentae Informaticae.  3--23, 1995.