ceta_eq: termination proof not accepted
1: error below switch to dependency pairs
1.1: error below the dependency graph processor
 1.1.1: error when applying the reduction pair processor to remove from the DP problem
  pairs:
  
  a__tail#(cons(X, XS)) -> mark#(XS)
  mark#(tail(X)) -> a__tail#(mark(X))
  mark#(tail(X)) -> mark#(X)
  mark#(cons(X1, X2)) -> mark#(X1)
  rules:
  
  a__tail(cons(X, XS)) -> mark(XS)
  a__tail(X) -> tail(X)
  a__zeros -> cons(0, zeros)
  a__zeros -> zeros
  mark(zeros) -> a__zeros
  mark(tail(X)) -> a__tail(mark(X))
  mark(cons(X1, X2)) -> cons(mark(X1), X2)
  mark(0) -> 0
  
   the pairs 
  a__tail#(cons(X, XS)) -> mark#(XS)
  mark#(tail(X)) -> mark#(X)
  mark#(cons(X1, X2)) -> mark#(X1)
  
  could not apply the generic root reduction pair processor with the following
  SCNP-version with mu = MAX and the level mapping defined by 
  pi(mark#) = [(1,0)]
  pi(a__tail#) = [(1,0)]
  Argument Filter: 
  pi(tail/1) = [1]
  pi(mark/1) = [1]
  pi(cons/2) = [1,2]
  pi(zeros/0) = []
  pi(a__zeros/0) = []
  pi(a__tail/1) = [1]
  pi(0/0) = []
  
  RPO with the following precedence
  precedence(tail[1]) = 4
  precedence(mark[1]) = 4
  precedence(cons[2]) = 0
  precedence(zeros[0]) = 1
  precedence(a__zeros[0]) = 3
  precedence(a__tail[1]) = 4
  precedence(0[0]) = 2
  
  precedence(_) = 0
  and the following status
  status(tail[1]) = mul
  status(mark[1]) = mul
  status(cons[2]) = mul
  status(zeros[0]) = mul
  status(a__zeros[0]) = mul
  status(a__tail[1]) = mul
  status(0[0]) = mul
  
  status(_) = lex
  
  problem when orienting (usable) rules
  could not orient mark(tail(X)) >= a__tail(mark(X))
  pi( mark(tail(X)) ) = mark(tail(X))
  pi( a__tail(mark(X)) ) = a__tail(mark(X))
  could not orient mark(tail(X)) >=RPO a__tail(mark(X))