Certification Problem
Input (TPDB TRS_Standard/AG01/#3.18)
The rewrite relation of the following TRS is considered.
|
minus(x,0) |
→ |
x |
(1) |
|
minus(s(x),s(y)) |
→ |
minus(x,y) |
(2) |
|
double(0) |
→ |
0 |
(3) |
|
double(s(x)) |
→ |
s(s(double(x))) |
(4) |
|
plus(0,y) |
→ |
y |
(5) |
|
plus(s(x),y) |
→ |
s(plus(x,y)) |
(6) |
|
plus(s(x),y) |
→ |
plus(x,s(y)) |
(7) |
|
plus(s(x),y) |
→ |
s(plus(minus(x,y),double(y))) |
(8) |
Property / Task
Prove or disprove termination.Answer / Result
Yes.Proof (by NaTT @ termCOMP 2023)
1 Dependency Pair Transformation
The following set of initial dependency pairs has been identified.
|
plus#(s(x),y) |
→ |
plus#(x,y) |
(9) |
|
plus#(s(x),y) |
→ |
double#(y) |
(10) |
|
double#(s(x)) |
→ |
double#(x) |
(11) |
|
plus#(s(x),y) |
→ |
minus#(x,y) |
(12) |
|
plus#(s(x),y) |
→ |
plus#(x,s(y)) |
(13) |
|
minus#(s(x),s(y)) |
→ |
minus#(x,y) |
(14) |
|
plus#(s(x),y) |
→ |
plus#(minus(x,y),double(y)) |
(15) |
1.1 Dependency Graph Processor
The dependency pairs are split into 3
components.
-
The
1st
component contains the
pair
|
plus#(s(x),y) |
→ |
plus#(minus(x,y),double(y)) |
(15) |
|
plus#(s(x),y) |
→ |
plus#(x,s(y)) |
(13) |
|
plus#(s(x),y) |
→ |
plus#(x,y) |
(9) |
1.1.1 Reduction Pair Processor with Usable Rules
Using the Max-polynomial interpretation
| [s(x1)] |
=
|
x1 + 2 |
| [minus(x1, x2)] |
=
|
x1 + 1 |
| [plus#(x1, x2)] |
=
|
x1 + 0 |
| [0] |
=
|
7721 |
| [double#(x1)] |
=
|
0 |
| [double(x1)] |
=
|
7720 |
| [minus#(x1, x2)] |
=
|
0 |
| [plus(x1, x2)] |
=
|
0 |
together with the usable
rules
|
minus(x,0) |
→ |
x |
(1) |
|
minus(s(x),s(y)) |
→ |
minus(x,y) |
(2) |
(w.r.t. the implicit argument filter of the reduction pair),
the
pairs
|
plus#(s(x),y) |
→ |
plus#(minus(x,y),double(y)) |
(15) |
|
plus#(s(x),y) |
→ |
plus#(x,s(y)) |
(13) |
|
plus#(s(x),y) |
→ |
plus#(x,y) |
(9) |
could be deleted.
1.1.1.1 Dependency Graph Processor
The dependency pairs are split into 0
components.
-
The
2nd
component contains the
pair
|
minus#(s(x),s(y)) |
→ |
minus#(x,y) |
(14) |
1.1.2 Reduction Pair Processor with Usable Rules
Using the Max-polynomial interpretation
| [s(x1)] |
=
|
x1 + 2 |
| [minus(x1, x2)] |
=
|
x1 + 1 |
| [plus#(x1, x2)] |
=
|
x1 + 0 |
| [0] |
=
|
7721 |
| [double#(x1)] |
=
|
0 |
| [double(x1)] |
=
|
7720 |
| [minus#(x1, x2)] |
=
|
x1 + x2 + 0 |
| [plus(x1, x2)] |
=
|
0 |
together with the usable
rules
|
minus(x,0) |
→ |
x |
(1) |
|
minus(s(x),s(y)) |
→ |
minus(x,y) |
(2) |
(w.r.t. the implicit argument filter of the reduction pair),
the
pair
|
minus#(s(x),s(y)) |
→ |
minus#(x,y) |
(14) |
could be deleted.
1.1.2.1 Dependency Graph Processor
The dependency pairs are split into 0
components.
-
The
3rd
component contains the
pair
|
double#(s(x)) |
→ |
double#(x) |
(11) |
1.1.3 Reduction Pair Processor with Usable Rules
Using the Max-polynomial interpretation
| [s(x1)] |
=
|
x1 + 1 |
| [minus(x1, x2)] |
=
|
x1 + 1 |
| [plus#(x1, x2)] |
=
|
x1 + 0 |
| [0] |
=
|
11294 |
| [double#(x1)] |
=
|
x1 + 0 |
| [double(x1)] |
=
|
11293 |
| [minus#(x1, x2)] |
=
|
0 |
| [plus(x1, x2)] |
=
|
0 |
together with the usable
rules
|
minus(x,0) |
→ |
x |
(1) |
|
minus(s(x),s(y)) |
→ |
minus(x,y) |
(2) |
(w.r.t. the implicit argument filter of the reduction pair),
the
pair
|
double#(s(x)) |
→ |
double#(x) |
(11) |
could be deleted.
1.1.3.1 Dependency Graph Processor
The dependency pairs are split into 0
components.