/export/starexec/sandbox/solver/bin/starexec_run_FirstOrder /export/starexec/sandbox/benchmark/theBenchmark.xml /export/starexec/sandbox/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 
  fib : [o] --> o 
  fibiter : [o * o * o * o] --> o 
  if : [o * o * o * o * o] --> o 
  lt : [o * o] --> o 
  plus : [o * o] --> o 
  s : [o] --> o 
  true : [] --> o 

  plus(0, X) => X 
  plus(s(X), Y) => s(plus(X, Y)) 
  lt(0, s(X)) => true 
  lt(X, 0) => false 
  lt(s(X), s(Y)) => lt(X, Y) 
  fib(X) => fibiter(X, 0, 0, s(0)) 
  fibiter(X, Y, Z, U) => if(lt(Y, X), X, Y, Z, U) 
  if(false, X, Y, Z, U) => Z 
  if(true, X, Y, Z, U) => fibiter(X, s(Y), U, plus(Z, U)) 

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 : [] --> wc 
  false : [] --> ub 
  fib : [wc] --> wc 
  fibiter : [wc * wc * wc * wc] --> wc 
  if : [ub * wc * wc * wc * wc] --> wc 
  lt : [wc * wc] --> ub 
  plus : [wc * wc] --> wc 
  s : [wc] --> wc 
  true : [] --> ub 


+++ 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.