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Howard Page-Clark Learn to Program using Lazarus BBBLLLAAAIIISSSEEE PPPAAASSSCCCAAALLL MMMAAAGGGAAAZZZIIINNNEEE PUBLISHER I Pascal Learn to program using Lazarus by Howard Page Clark II Learn to program using Lazarus Developmental Editor: Detlef Overbeek Production Editor: Detlef Overbeek Proofreaders: Peter Bijlsma, Correctors: Detlef Overbeek Cover Designer: Detlef Overbeek Copyright © 2013 by Blaise Pascal Magazine Copyright © 2012. All rights reserved by Blaise Pascal Magazine Email: [email protected] http://www.blaisepascalmagazine.eu Blaise Pascal Magazine grants readers limited permission to reuse the code found in this publication so long as the author(s) are attributed in any application containing the reusable code and the code itself is never distributed, posted online by electronic transmission, sold, or commercially exploited as a stand- alone product. Aside from this specific exception concerning reusable code, no part of this publication may be stored in a retrieval system, transmitted, or reproduced in any way, including but not limited to photocopy, photograph, magnetic, or other record, without the prior agreement and written permission of the publisher. This edition is registered by the Dutch Royal Library Nederlandse Koninklijke Bibliotheek ISBN: 978-94-90968-04-5 Blaise Pascal Magazine and the Blaise Pascal Magazine logo are either registered trademarks or trademarks of the Pro Pascal Foundation in the Netherlands and/or other countries. TRADEMARKS: Blaise Pascal Magazine has attempted throughout this book to distinguish proprietary trademarks from descriptive terms by following the capitalization style used by the manufacturer. The authors and publisher have used their best efforts in producing this book, whose content is based on the latest software releases wherever possible. Portions of the manuscript may be based upon pre-release versions supplied by software manufacturer(s). The authors and the publisher make no representation or warranties of any kind with regard to the completeness or accuracy of the contents herein and accept no liability of any kind including but not limited to performance, merchantability, fitness for any particular purpose, or any losses or damages of any kind caused or alleged to be caused directly or indirectly from this book. III Foreword Learn to program using Lazarus Pascal is enjoying something of a revival, and this is due in no small part to the quality and success of the Free Pascal Compiler, and the Lazarus project, which depends on it. That success, in turn, owes much to the skill and dedication of the core team members of the two projects. This book is a tribute to the guys (so far there are no significant gals) starting with Florian Klaempfl who have carried the development of these projects to the significant phase each has reached. One measure of the lasting value of open source projects is the quality of the programming communities that are drawn together through participation in such projects, and both Free Pascal and Lazarus shine in this respect. I share the passion of a few in the programming community for good documentation, and particularly for material which makes programming more accessible to newcomers or those who (like me) don't have a formal education in information technology or computer science. The Pascal language came to birth in the imagination of a Swiss software architect, a rare academic who values clarity and simplicity enough to make both aspects a hallmark of his designs. Pascal later became a widely available compiler (for CP/M, DOS and then Windows) largely through a Danish software architect. Borland incorporated that Danish compiler into an IDE, where Anders Hejlsberg and Chuck Jazdzewski among others oversaw adaptation of the language and support libraries for GUI programming on Windows. Part of Free Pascal's achievement has been to liberate Pascal from its attachment principally to the Windows/.NET platform (which characterised the major years of US-based Object Pascal Delphi development, since the Kylix fork was not maintained). It was FPC (for a time) that enabled the Delphi IDE to generate code to run on iOS. A maturing Lazarus has also helped slowly to convince developers for MacOS, Linux and more recently Android and other platforms that Pascal can truly serve their needs. I am grateful to Mattias Gaertner, who encouraged me to write this book during our first conversation, to Michaël van Canneyt, who saw an early draft of the manuscript and whose incisive comments helped enormously in shaping the organisation of the material, and to Detlef Overbeek, whose generous hospitality enabled me to see the obvious enthusiasm for Pascal development among programmers gathered in Utrecht. He is a friend who is ready to take risks in publishing. Mistakes you find in the following pages are, of course, mine alone. I would be grateful for notification of any needed corrections, so that they can be included in any future printing. Please direct any comments to me via the publisher's website: www.blaisepascal.eu Howard Page-Clark Christmas 2012 IV Learn to program using Lazarus V Contents Learn to program using Lazarus CHAPTER 1 STARTING TO PROGRAM 1.a What to expect in this book 1 1.b What is programming? 1 1.c The worlds inside and outside the CPU 2 1.d Not only digital data, but also digital code 3 1.e Different computer languages at different levels 3 1.f Pascal: a universal computer language 4 1.g Lazarus: an IDE for Pascal 5 1.h An open source approach to software 6 1.i Getting help 7 1.j Review Questions 8 CHAPTER 2 LAZARUS AND PASCAL 2.a The layout of the Lazarus IDE 9 2.b Two different sorts of program 10 2.c Writing, compiling and running firstproject 12 2.d The structure of a Pascal program 14 2.e Comments in Pascal code 16 2.f Use of names in Pascal 16 2.g Compiler directives 17 2.h Review Questions 18 CHAPTER 3 TYPES, VARIABLES, CONSTANTS AND ASSIGNMENTS 3.a Pascal types 19 3.b Ordinal types 20 3.c The boolean type 21 3.d Enumerated types 22 3.e Type conversion 24 3.f Typecasts 25 3.g Variables 26 3.h Initialised variables 26 3.i Assignment: placing a value in a variable 27 3.j Extended numerical assignment operators 28 3.k Constants and literal values 28 3.l A program example: simple_types 29 3.m Typed constants 31 3.n Pointers 33 3.o Review Questions 35 CHAPTER 4 STRUCTURED TYPES 4.a Static arrays 36 4.b Unnamed (anonymous) types 37 4.c Pascal shortstrings 38 4.d Dynamic arrays 39 4.e Ansistrings 39 4.f Records 41 4.g The with . . . do statement 42 4.h Set types 44 4.i Binary files 45 4.j Text files 47 4.k Review Questions 48 VI Contents Learn to program using Lazarus CHAPTER 5 EXPRESSIONS AND OPERATORS 5.a Operators: forming Pascal expressions 49 5.b Mathematical operators 49 5.c Boolean operators: not, and, or, xor 50 5.d Comparison (relational) operators 50 5.e Bitwise (logical) operators 51 5.f A program example: simple_expressions 51 5.g Review Questions 52 CHAPTER 6 PASCAL STATEMENTS 6.a Conditional statement: if 54 6.b Conditional statement: case of end 55 6.c Looping statement: for to do 56 6.d Looping statement: for downto do ; Break and Continue 57 6.e Looping statement: for in do 57 6.f Looping statement: while do 58 6.g Looping statement: repeat until 58 6.h Exception statements: raise, on, try 58 6.i Review Exercises 61 CHAPTER 7 ROUTINES: FUNCTIONS AND PROCEDURES 7.a Routines and methods 62 7.b Calling a routine 62 7.c Passing data to a routine: parameters 63 7.d Picking up the value returned from a function 63 7.e Parameter classification: var, const, out 64 7.f Default parameters 65 7.g Declaring procedures and functions 65 7.h A program example: function_procedure 66 7.i The Exit() procedure 66 7.j Review Questions 68 CHAPTER 8 CLASS: AN ELABORATE TYPE 8.a Generations of classes 69 8.b Class data fields 70 8.c Class memory management 71 8.d Exercising simple class methods 73 8.e Properties: special access to class data and events 75 8.f Private, protected, public and published 80 8.g Events 81 8.h Event properties 83 8.i Object oriented design 85 8.j Review Exercises 85 CHAPTER 9 POLYMORPHISM 9.a Cross-platform polymorphism 86 9.b Polymorphic methods in classes 87 9.c Polymorphic graphic classes 89 9.d Overloading 94 9.e Default parameters 95 9.f Review Questions 95 VII Contents Learn to program using Lazarus CHAPTER 10 UNITS, GUI PROGRAMS AND THE IDE 10.a Unit structure and scope 96 10.b The GUI program skeleton 99 10.c Packages 101 10.d Changing the program icon 101 10.e The main form file 102 10.f Editor Auto-completion 103 10.g Using the Designer 106 10.h The Object Inspector 107 10.i OI Favorites and shortcuts 109 10.j The OI Restricted page 110 10.k The Component Palette 111 10.l Finding a Palette component 111 10.m Regular, DB and RTTI component types 112 10.n Non-visual LCL and FCL support classes 113 10.o Review Exercises 113 CHAPTER 11 DISPLAY CONTROLS 11.a Display controls: TLabel 114 11.b Display controls: exploring TLabel properties 115 11.c Display controls: TStaticText 119 11.d Display controls: TBevel and TDividerBevel 120 11.e Display controls: TListBox 121 11.f Display controls: TStatusBar 122 11.g Display controls: further options 123 11.h Review Questions 123 CHAPTER 12 GUI EDIT CONTROLS 12.a Editing short phrases: TEdit and TLabeledEdit 124 12.b Editing or choosing short phrases: TComboBox 126 12.c Editing integers and floating point numbers 126 12.d Multiple-line editors 129 12.e A component browser 130 12.f Getting RTTI information for a component 135 12.g Adding external tools to the IDE 138 12.h Review Questions 140 CHAPTER 13 LAZARUS GUI PROJECTS 13.a Planning a project 141 13.b Creating a project task list 141 13.c ToDo functionality 142 13.d Version control 142 13.e Test-driven software development 142 13.f Naming 143 13.g Project directory structure 143 13.h A template project: SetDemo 144 13.i Encapsulating set interaction within a new class 146 13.j The setdemo UI 149 13.k Review Questions 156 VIII Contents Learn to program using Lazarus CHAPTER 14 COMPONENT CONTAINERS 14.a Non-visual RTL classes 157 14.b Creating new forms 158 14.c Ownership and Parentage 160 14.d Programmatic form creation 160 14.e TGroupBox, TPanel 163 14.f Resizeable children 164 14.g TFrame 166 14.h TDatamodule 167 14.i Review Exercises 167 CHAPTER 15 NON-VISUAL GUI SUPPORT CLASSES 15.a TPersistent descendants 168 15.b A chemical TCollection 169 15.c The TStringList class 172 15.d Sorting lines in a text file 173 15.e Streams 176 15.f TFileStream 177 15.g TMemoryStream, TStringStream and Blowfish 180 15.h Visualising a stream 182 15.i Review Exercises 187 CHAPTER 16 FILES AND ERRORS 16.a File access in Pascal 188 16.b Run-time errors and exceptions 188 16.c An example of string error-handling 189 16.d File name encoding issues 192 16.e User-directed file searching and naming – the Dialogs Palette page 193 16.f Discriminating between text and binary files 196 CHAPTER 17 WORKING WITHIN KNOWN LIMITS 17.a Using recursion to evaluate factorials 200 17.b Catching a specific exception 203 17.c Permutations 204 17.d Time-consuming routines 205 17.e Generating anagrams 206 17.f Review Questions 210 CHAPTER 18 ALGORITHMS AND UNIT TESTS 18.a Collaboration 211 18.b The algorithm – a specific plan 211 18.c A parsing algorithm 212 18.d Testing the ParseToWords function: the FPCUnit Test 215 18.e Example tests 218 18.f Test-driven development 220 18.g Optimising debugged routines 220 18.h Profiling and compiler optimisation 220 18.i Review Questions 221 IX