| 1: | concat(leaf,y) | → y | |
| 2: | concat(cons(u,v),y) | → cons(u,concat(v,y)) | |
| 3: | less_leaves(x,leaf) | → false | |
| 4: | less_leaves(leaf,cons(w,z)) | → true | |
| 5: | less_leaves(cons(u,v),cons(w,z)) | → less_leaves(concat(u,v),concat(w,z)) | |
| 6: | CONCAT(cons(u,v),y) | → CONCAT(v,y) | |
| 7: | LESS_LEAVES(cons(u,v),cons(w,z)) | → LESS_LEAVES(concat(u,v),concat(w,z)) | |
| 8: | LESS_LEAVES(cons(u,v),cons(w,z)) | → CONCAT(u,v) | |
| 9: | LESS_LEAVES(cons(u,v),cons(w,z)) | → CONCAT(w,z) | |