| 1: | p(0) | → 0 | |
| 2: | p(s(X)) | → X | |
| 3: | leq(0,Y) | → true | |
| 4: | leq(s(X),0) | → false | |
| 5: | leq(s(X),s(Y)) | → leq(X,Y) | |
| 6: | if(true,X,Y) | → X | |
| 7: | if(false,X,Y) | → Y | |
| 8: | diff(X,Y) | → if(leq(X,Y),0,s(diff(p(X),Y))) | |
| 9: | LEQ(s(X),s(Y)) | → LEQ(X,Y) | |
| 10: | DIFF(X,Y) | → IF(leq(X,Y),0,s(diff(p(X),Y))) | |
| 11: | DIFF(X,Y) | → LEQ(X,Y) | |
| 12: | DIFF(X,Y) | → DIFF(p(X),Y) | |
| 13: | DIFF(X,Y) | → P(X) | |