Peg Solitaire tutorial

Template:newpage This tutorial is the second Lazarus tutorial that aims at introducing the basics of Lazarus application development. It's best to start this tutorial after having finished the first one (Howdy_World_(Hello_World_on_steroids)). This tutorial exlpains a bit about how to work with graphics and how to make a program modular. The final product of this tutorial is a basic but working version of the Peg Solitaire game ([1]). If all goes well in the end it will look something like this:

Start the project

As mentioned in the previous tutorial it's best to start with a clean, separate directory for each project. A quick recap:

• Create a new directory for this game.
• Start a new Application (Project/New Project... and select Application).
• In the project options insert bin\ in front of the target filename.
• Save the project as PegSolitaire.
• Save the main form as ufrmMain.
• In the object inspector change the form's name to frmMain.
• Change the caption to Lazarus Peg Solitaire.

And extra for this project:

• Open the project options dialog (Shift-Ctrl-F11).
• Select Compiler Options/Code Generation.
• Enable Range checking and Overflow error checking (see image belows).

First steps

It's always a good idea to seperate gui related code from data structure definitions. So the first step will be the creation of a separate unit for our Solitaire data structures.

• From the menu choose File/New Unit....
• Save the unit as PegDatastructures (and press the lowercase button that pop's up).

The basic elements of a Peg Solitaire board are the marbles, the board structure and the empy places. We'll simulate this by a simple matrix that has cells of a certain type (empty, occupied and not accessible). And we'll encapsulate all this in a class that handles all the data manipulation.

• Add the following code to the PegDatastructures unit.

<Delphi>const

 C_MAX = 7;  // Max board size: 7x7

type

 TCellNums = 1..C_MAX;
 TCellType = (ctNoAccess, ctEmpty, ctPeg);
 TPegCells = array[TCellNums, TCellNums] of TCellType;

 TPegSolitaire = class
 private
   Size: TCellNums;
   PegCells: TPegCells;
   
 public
   constructor Create(const pSize: TCellNums);
 end;</Delphi>

... 2 be continued...