queue-class: A Queue Class

Description

A queue implementation using a filehash database

Usage

createQ(filename)
initQ(filename)
pop(db, ...)
push(db, val, ...)
isEmpty(db, ...)
top(db, ...)
# S4 method for queue
show(object)
# S4 method for queue
push(db, val, ...)
# S4 method for queue
isEmpty(db)
# S4 method for queue
top(db, ...)
# S4 method for queue
pop(db, ...)

Value

createQ and initQ return a queue object

Arguments

filename: name of queue file
db: a queue object
...: arguments passed to other methods
val: an R object to be added to the tail queue
object: a queue object

Methods (by generic)

show(queue): Print a queue object
push(queue): adds an element to the tail ("bottom") of the queue
isEmpty(queue): returns TRUE/FALSE depending on whether there are elements in the queue.
top(queue): returns the value of the "top" (i.e. head) of the queue; an error is signaled if the queue is empty
pop(queue): returns the value of the "top" (i.e. head) of the queue and subsequently removes that element from the queue; an error is signaled if the queue is empty

Functions

createQ(): Create a file-based queue object
initQ(): Intialize an existing queue object
pop(): Return (and remove) the top element of a queue
push(): Push an R object on to the tail of a queue
isEmpty(): Check if a queue is empty or not
top(): Return the top of the queue

Slots

queue: Object of class "filehashDB1"

name

Object of class "character": the name of the queue (default is the file name in which the queue data are stored)

Details

Objects can be created by calls of the form new("queue", ...) or by calling createQ. Existing queues can be initialized with initQ.