Functions for interacting with stack and queue data structures
implemented using filehash databases.
push(db, val, ...)
mpush(db, vals, ...)
pop(db, ...)
top(db, ...)
isEmpty(db, ...)an object of class "stack" or "queue"
an R object
a list of R objects
arguments passed to other methods
push and mpush return nothing useful; pop returns
a value from the stack/queue and deletes that value from the
stack/queue; top returns the "top" value from the stack/queue;
isEmpty returns TRUE/FALSE depending on whether
the stack/queue is empty or not. Both pop and top
signal an error if the stack/queue is empty.
Note that for mpush, if vals is not a list it will be
coerced to a list via as.list. Currently, mpush is only
implemented for "stack"s.