| Symbol | Specification | Kind | Type |
|---|---|---|---|
| . .t | treeorfail | f | treeorfail → tree |
| fail | treeorfail | c | treeorfail |
| l | tree | f | tree → tree |
| Leaf | tree | c | tree |
| Node | tree | f | tree × tree → tree |
| r | tree | f | tree → tree |
| some | treeorfail | f | tree → treeorfail |
| t | tree | v | tree |
| t0 | tree | v | tree |
| t1 | tree | v | tree |
| t2 | tree | v | tree |
| to | treeorfail | v | treeorfail |
| to0 | treeorfail | v | treeorfail |
| to1 | treeorfail | v | treeorfail |
| tree | tree | s | |
| treeorfail | treeorfail | s |