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_size                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