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# struct::set(n) 2.2.3 "Tcl Data Structures"

## Name

struct::set - Procedures for manipulating sets

## Synopsis

- package require
**Tcl 8.0** - package require
**struct::set ?2.2.3?**

**::struct::set****empty***set***::struct::set****size***set***::struct::set****contains***set**item***::struct::set****union**?*set1*...?**::struct::set****intersect**?*set1*...?**::struct::set****difference***set1**set2***::struct::set****symdiff***set1**set2***::struct::set****intersect3***set1**set2***::struct::set****equal***set1**set2***::struct::set****include***svar**item***::struct::set****exclude***svar**item***::struct::set****add***svar**set***::struct::set****subtract***svar**set***::struct::set****subsetof***A**B*

## Description

The **::struct::set** namespace contains several
useful commands for processing finite sets.

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

*Note:* As of version 2.2 of this package a critcl based
C implementation is available. This implementation however requires
Tcl 8.4 to run.

## COMMANDS

**::struct::set****empty***set*-
Returns a boolean value indicating if the

*set*is empty (**true**), or not (**false**). **::struct::set****size***set*-
Returns an integer number greater than or equal to zero. This is the number of elements in the

*set*. In other words, its cardinality. **::struct::set****contains***set**item*-
Returns a boolean value indicating if the

*set*contains the element*item*(**true**), or not (**false**). **::struct::set****union**?*set1*...?-
Computes the set containing the union of

*set1*,*set2*, etc., i.e. "*set1*+*set2*+ ...", and returns this set as the result of the command. **::struct::set****intersect**?*set1*...?-
Computes the set containing the intersection of

*set1*,*set2*, etc., i.e. "*set1***set2** ...", and returns this set as the result of the command. **::struct::set****difference***set1**set2*-
Computes the set containing the difference of

*set1*and*set2*, i.e. ("*set1*-*set2*") and returns this set as the result of the command. **::struct::set****symdiff***set1**set2*-
Computes the set containing the symmetric difference of

*set1*and*set2*, i.e. ("(*set1*-*set2*) + (*set2*-*set1*)") and returns this set as the result of the command. **::struct::set****intersect3***set1**set2*-
This command is a combination of the methods

**intersect**and**difference**. It returns a three-element list containing "*set1***set2*", "*set1*-*set2*", and "*set2*-*set1*", in this order. In other words, the intersection of the two parameter sets, and their differences. **::struct::set****equal***set1**set2*-
Returns a boolean value indicating if the two sets are equal (

**true**) or not (**false**). **::struct::set****include***svar**item*-
The element

*item*is added to the set specified by the variable name in*svar*. The return value of the command is empty. This is the equivalent of**lappend**for sets. If the variable named by*svar*does not exist it will be created. **::struct::set****exclude***svar**item*-
The element

*item*is removed from the set specified by the variable name in*svar*. The return value of the command is empty. This is a near-equivalent of**lreplace**for sets. **::struct::set****add***svar**set*-
All the element of

*set*are added to the set specified by the variable name in*svar*. The return value of the command is empty. This is like the method**include**, but for the addition of a whole set. If the variable named by*svar*does not exist it will be created. **::struct::set****subtract***svar**set*-
All the element of

*set*are removed from the set specified by the variable name in*svar*. The return value of the command is empty. This is like the method**exclude**, but for the removal of a whole set. **::struct::set****subsetof***A**B*-
Returns a boolean value indicating if the set

*A*is a true subset of or equal to the set*B*(**true**), or not (**false**).

## Bugs, Ideas, Feedback

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

## Keywords

cardinality, difference, emptiness, exclusion, inclusion, intersection, membership, set, symmetric difference, union

## Category

Data structures

## Copyright

Copyright © 2004-2008 Andreas Kupries <andreas_kupries@users.sourceforge.net>