# struct::set(3tcl) 2.2.5 struct "Tcl Data Structures"

## Name

struct::set - Procedures for manipulating sets

## Synopsis

- package require Tcl 8.5 9
- package require struct::set ?2.2.4?

- ::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).

## REFERENCES

## 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.

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

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>