Certification Problem

Input (TPDB TRS_Standard/SK90/2.38)

The rewrite relation of the following TRS is considered.

++(nil,y) y (1)
++(x,nil) x (2)
++(.(x,y),z) .(x,++(y,z)) (3)
++(++(x,y),z) ++(x,++(y,z)) (4)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by AProVE @ termCOMP 2023)

1 Rule Removal

Using the Knuth Bendix order with w0 = 1 and the following precedence and weight functions
prec(nil) = 0 weight(nil) = 1
prec(++) = 2 weight(++) = 0
prec(.) = 1 weight(.) = 0
all of the following rules can be deleted.
++(nil,y) y (1)
++(x,nil) x (2)
++(.(x,y),z) .(x,++(y,z)) (3)
++(++(x,y),z) ++(x,++(y,z)) (4)

1.1 R is empty

There are no rules in the TRS. Hence, it is terminating.