Returns a possibly filtered and possibly transformed list
of the elements in a container. If the container uses nodes, then the elements are
the things 'in' the nodes.
| collect-elements < array > |
| collect-elements :around < > |
| collect-elements < hash-table > |
| collect-elements < > |
| collect-elements < list > |
| collect-elements < > |
| collect-elements < > |
| collect-elements < vector > |