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# struct::prioqueue(n) 1.5 tcllib "Tcl Data Structures"

## Name

struct::prioqueue - Create and manipulate prioqueue objects

## Synopsis

- package require Tcl 8.5 9
- package require struct::prioqueue ?1.5?

- ::struct::prioqueue ?-ascii|-dictionary|-integer|-real? ?prioqueueName?
- prioqueueName option ?arg arg ...?
- prioqueueName clear
- prioqueueName remove item
- prioqueueName destroy
- prioqueueName get ?count?
- prioqueueName peek ?count?
- prioqueueName peekpriority ?count?
- prioqueueName put item prio ?item prio ...?
- prioqueueName size

## Description

This package implements a simple priority queue using nested tcl lists.

The command ::struct::prioqueue creates a new priority queue with default priority key type -integer. This means that keys given to the put subcommand must have this type.

This also sets the priority ordering. For key types -ascii and -dictionary the data is sorted in ascending order (as with lsort -increasing), thereas for -integer and -real the data is sorted in descending order (as with lsort -decreasing).

Prioqueue names are unrestricted, but may be recognized as options if no priority type is given.

::struct::prioqueue ?-ascii|-dictionary|-integer|-real? ?prioqueueName?

  The ::struct::prioqueue command creates a new prioqueue object with an associated global Tcl command whose name is prioqueueName. This command may be used to invoke various operations on the prioqueue. It has the following general form:

prioqueueName option ?arg arg ...?

  option and the args determine the exact behavior of the command. The following commands are possible for prioqueue objects:

prioqueueName clear

  Remove all items from the prioqueue.

prioqueueName remove item

  Remove the selected item from this priority queue.

prioqueueName destroy

  Destroy the prioqueue, including its storage space and associated command.

prioqueueName get ?count?

  Return the front count items of the prioqueue (but not their priorities) and remove them from the prioqueue. If count is not specified, it defaults to 1. If count is 1, the result is a simple string; otherwise, it is a list. If specified, count must be greater than or equal to 1. If there are no or too few items in the prioqueue, this command will throw an error.

prioqueueName peek ?count?

  Return the front count items of the prioqueue (but not their priorities), without removing them from the prioqueue. If count is not specified, it defaults to 1. If count is 1, the result is a simple string; otherwise, it is a list. If specified, count must be greater than or equal to 1. If there are no or too few items in the queue, this command will throw an error.

prioqueueName peekpriority ?count?

  Return the front count items priority keys, without removing them from the prioqueue. If count is not specified, it defaults to 1. If count is 1, the result is a simple string; otherwise, it is a list. If specified, count must be greater than or equal to 1. If there are no or too few items in the queue, this command will throw an error.

prioqueueName put item prio ?item prio ...?

  Put the item or items specified into the prioqueue. prio must be a valid priority key for this type of prioqueue, otherwise an error is thrown and no item is added. Items are inserted at their priority ranking. Items with equal priority are added in the order they were added.

prioqueueName size

  Return the number of items in the prioqueue.

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category struct :: prioqueue of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## Keywords

ordered list, prioqueue, priority queue

## Category

Data structures

## Copyright

Copyright © 2003 Michael Schlenker <mic42@users.sourceforge.net>