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


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YES
We consider the system theBenchmark.

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

  a : [] --> o 
  f : [o * o] --> o 

  f(a, f(f(a, X), a)) => f(f(a, f(a, X)), a) 

We use rule removal, following [Kop12, Theorem 2.23].

This gives the following requirements (possibly using Theorems 2.25 and 2.26 in [Kop12]):

  f(a, f(f(a, X), a)) >? f(f(a, f(a, X)), a) 

We orient these requirements with a polynomial interpretation in the natural numbers.

The following interpretation satisfies the requirements:

  a = 3 
  f = \y0y1.1 + y0 + 3y1 

Using this interpretation, the requirements translate to:

  [[f(a, f(f(a, _x0), a))]] = 46 + 9x0 > 26 + 9x0 = [[f(f(a, f(a, _x0)), a)]] 

We can thus remove the following rules:

  f(a, f(f(a, X), a)) => f(f(a, f(a, X)), a) 

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.


+++ Citations +++

[Kop12]  C. Kop.  Higher Order Termination.  PhD Thesis, 2012.