Certification Problem

Input (TPDB TRS_Standard/SK90/4.31)

The rewrite relation of the following TRS is considered.

purge(nil) nil (1)
purge(.(x,y)) .(x,purge(remove(x,y))) (2)
remove(x,nil) nil (3)
remove(x,.(y,z)) if(=(x,y),remove(x,z),.(y,remove(x,z))) (4)

Property / Task

Prove or disprove termination.

Answer / Result

Yes.

Proof (by ttt2 @ termCOMP 2023)

1 Dependency Pair Transformation

The following set of initial dependency pairs has been identified.
purge#(.(x,y)) remove#(x,y) (5)
purge#(.(x,y)) purge#(remove(x,y)) (6)
remove#(x,.(y,z)) remove#(x,z) (7)

1.1 Dependency Graph Processor

The dependency pairs are split into 1 component.