Guia de prolog

A Beginners' Guide to Visual Prolog
Version 7.2

Thomas W. de Boer

Version of this book: 1.1

Preface

There is a beautiful programming language out there. It is called Prolog. Originally the language Prolog was created by Calmeraur it was popularized by famous books by Clocksin & Mellish and by Ivan Bratko and brought to the masses by software producer Borland who sold Turbo Prologfor MsDos systems. But the masses didn’t buy it and Borland stopped selling Turbo Prolog. That was long ago. After a few years it became apparent that the makers of Turbo Prolog had returned to Denmark and started the company PDC: the Prolog Development Company. They put years of effort into their dialect of the language and now there is Visual Prolog. It is object-oriented, it has a Graphical UserInterface, it has a Integrated Development Environment. And it still has the charm and elegance of the language they call Prolog. Formerly the great problem in learning Prolog was that you had to master the very different thinking of a declarative programming language. Once you’ve mastered it, it is a great way to write computer programs, so the effort was and is worthwhile. But nowadays it is notonly mastering a declarative language, there are these other aspects of a modern programming language: object-orientation, graphical user interface, et cetera. This book is an effort to tell you all about it. This book is an introduction. It is meant for people who know little about programming. It is not for people that know nothing. You should know the basics about computers and that it ispossible to program them and that for a program you use a programming language. But nowadays these things seem to bee widely known - even among computer nitwits. What when you know more? Then you should look for other sources. • When you are programmer and know about other languages like Visual Basic or C##, read the book Prolog for Tyros by Eduardo Costa. • When you know about other languages and arecurious about Prolog, read the articles by Thomas Linder Puls and Sabu Francis at the Visual Prolog web site at www.pdc.dk. • When you have experience in Prolog programming, look for details about Visual Prolog, object orientation in the advanced tutorials at the same web site. You will find the publications at the website: www.pdc.dk -> Solutions -> Visual Prolog -> Tutorials. At that site youwill also find a Wiki on programming in Visual Prolog There is a lot available about Visual Prolog. But for a beginner it is very hard to find his way through all the material. This book tries to bring structure in the apparent chaos for the beginner. I edited this book by borrowing and rewriting texts from other people (with their consent) and by filling in some gaps with old material that I wroteyears ago. It all comes together in this introductory text. I have tried to keep the content as low profile as possible, so even beginners can use it. But if you think that some things are not understandable, please let me know. You can reach me at t.w.de.boer@gmail.com. Groningen, Summer 2009. Thomas W. De Boer

Contents Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Chapter 1 The Integrated Development Environment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.1 The Integrated Development Environment IDE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.2 Creating a project in VIP. . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Chapter 2 Forms.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Create a form. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Enable the Task Menu option. . . . . . ....