2 A First Session with GAP

This tutorial introduces you to the GAP system. It is written with users in mind who have just managed to start GAP for the first time on their computer and want to learn the basic facts about GAP by playing around with some instructive examples. Therefore, this tutorial contains at many places several lines of input (which you should type on your terminal) followed by the corresponding output (which GAP produces as an answer to your input). 

This ``session protocol'' is indented and printed in typewriter style
(like this paragraph) in this tutorial and should look exactly as it
looks on your text terminal or text window.
This is to encourage you to actually run through these examples on your computer. This will support your feeling for GAP as a tool, which is the leading aim of this tutorial. Do not believe any statement in it as long as you cannot verify it for your own version of GAP. You will learn to distinguish between small deviations of the behavior of your personal GAP from the printed examples and serious nonsense.

Since the printing routines of GAP are in some sense machine dependent you will for instance encounter a different layout of the printed objects in different environments. But the contents should always be the same. In case you encounter serious nonsense it is highly recommended that you send a bug report to gap-trouble@dcs.st-and.ac.uk.

The examples in this tutorial should explain everything you have to know in order to be able to use GAP. The reference manual then gives a more systematic treatment of the various types of objects that GAP can manipulate. It seems desirable neither to start this systematic course with the most elementary (and most boring) structures, nor to confront you with all the complex data types before you know how they are composed from elementary structures. For this reason this tutorial wants to provide you with a basic understanding of GAP objects, on which the reference manual will then build when it explains everything in detail. So after having mastered this tutorial, you can immediately plunge into the exciting parts of GAP and only read detailed information about elementary things (in the reference manual) when you really need them.

Each chapter of this tutorial contains an overview of its sections at the beginning, and a section with references to the reference manual at the end.

Sections

  1. Starting and Leaving GAP
  2. The Read Evaluate Print Loop
  3. Constants and Operators
  4. Variables versus Objects
  5. Objects vs. Elements
  6. About Functions
  7. The Help System
  8. Further Information introducing the System

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GAP 4 manual
February 2000