Zap Game: do/while Loop

References:

• Pre-requisite: it is assumed that you have read through the prior tutorials, and are familiar with the concepts covered in those tutorials.

Goals:

• In this tutorial, we will:
  • Examine the do...while loop

1. Obtain the example code

• Here is the zip file to the source files and compiled executable of this example.
• Here is the keyboard mapping for the XBOX 360 controller.  
• Here is the main tutorial page for working with XNACS1Lib, and here is the complete documentation of the library: html-page or compiled html help file .

When the game starts, you'll see a screen that looks similar to this:

This version of the 'zap' game looks and plays identically to the prior version, which was explained in the 160 tutorial .

The only difference, code-wise, between this version and the prior version is that this version uses a do...while loop, instead of a normal while loop.

2. Examining The Program:

Let's examine the C# source code that produces the behavior we see on-screen

• Drawing the Hero's Laser in UpdateWorld():

  Version of code in 160 tutorial	Version of code in this tutorial
  XNACS1Circle lastCircle = null; Vector2 HeroBeam = m_Hero.Center; while (HeroBeam.X <= m_Enemy.CenterX) {     HeroBeam.X += 1f;     lastCircle = CreateHeroPath(HeroBeam); }	XNACS1Circle lastCircle = null; Vector2 HeroBeam = m_Hero.Center; do {     HeroBeam.X += 1f;     lastCircle = CreateHeroPath(HeroBeam); } while (HeroBeam.X < m_Enemy.CenterX);

  • In order to emphasize the differences between the code provided in the 160 tutorial, and the code provided in this tutorial, we have aligned the loop from the 'hero zapping' region side-by-side, with the new loop in this tutorial on the right.  Notice that there is literally only two lines of difference between them.
  • In this case, because we want to draw at least one circle, it's safe for us to use the ' do...while ' loop, which you have seen previously.

FURTHER EXERCISES::  

1. Go back to the 160 tutorial, and redo those exercises, using do...while loop(s).

	This work is supported in part by a grant from Microsoft Research under the Computer Gaming Curriculum in Computer Science RFP, Award Number 15871 and 16531.
2/8/2010