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# struct::stack(n) 1.5.3 tcllib "Tcl Data Structures"

## Name

struct::stack - Create and manipulate stack objects

## Synopsis

- package require Tcl 8.4
- package require struct::stack ?1.5.3?

- stackName option ?arg arg ...?
- stackName clear
- stackName destroy
- stackName get
- stackName getr
- stackName peek ?count?
- stackName peekr ?count?
- stackName trim ?newsize?
- stackName trim* ?newsize?
- stackName pop ?count?
- stackName push item ?item...?
- stackName size

## Description

The ::struct namespace contains a commands for processing finite stacks.

It exports a single command, ::struct::stack. All functionality provided here can be reached through a subcommand of this command.

Note: As of version 1.3.3 of this package a critcl based C implementation is available. This implementation however requires Tcl 8.4 to run.

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

stackName option ?arg arg ...?

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

stackName clear

  Remove all items from the stack.

stackName destroy

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

stackName get

  Returns the whole contents of the stack as a list, without removing them from the stack.

stackName getr

  A variant of get, which returns the contents in reversed order.

stackName peek ?count?

  Return the top count items of the stack, without removing them from the stack. 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 not enoughs items on the stack to fulfull the request, this command will throw an error.

stackName peekr ?count?

  A variant of peek, which returns the items in reversed order.

stackName trim ?newsize?

  Shrinks the stack to contain at most newsize elements and returns a list containing the elements which were removed. Nothing is done if the stack is already at the specified size, or smaller. In that case the result is the empty list.

stackName trim* ?newsize?

  A variant of trim which performs the shrinking, but does not return the removed elements.

stackName pop ?count?

  Return the top count items of the stack, and remove them from the stack. 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 not enoughs items on the stack to fulfull the request, this command will throw an error.

stackName push item ?item...?

  Push the item or items specified onto the stack. If more than one item is given, they will be pushed in the order they are listed.

stackName size

  Return the number of items on the stack.

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category struct :: stack 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

graph, matrix, queue, tree

## Category

Data structures