| ast | Display the abstract syntax tree | 
| cst | Call stack tree | 
| mem_used | How much memory is currently used by R? | 
| obj_addr | Find memory location of objects and their children. | 
| obj_addrs | Find memory location of objects and their children. | 
| obj_size | Calculate the size of an object. | 
| obj_sizes | Calculate the size of an object. | 
| ref | Display tree of references | 
| sxp | Inspect an object | 
| tree | Pretty tree-like object printing | 
| tree_label | Build element or node label in tree |