The rewrite relation of the following TRS is considered.
| U31(tt) | → | N | (1) |
| U42(tt) | → | s(plus(N,M)) | (2) |
| U11(tt) | → | U12(isNat) | (3) |
| U12(tt) | → | tt | (4) |
| U21(tt) | → | tt | (5) |
| U41(tt) | → | U42(isNat) | (6) |
| isNat | → | tt | (7) |
| isNat | → | U11(isNat) | (8) |
| isNat | → | U21(isNat) | (9) |
| plus(N,0) | → | U31(isNat) | (10) |
| plus(N,s(M)) | → | U41(isNat) | (11) |
The TRS violates one of the two variable conditions. Thus, it is not terminating.