Newsgroups: comp.os.msdos.djgpp
From: mheumann AT hotbot DOT com (Manni Heumann)
Subject: Re: Having problem with Allegro... need help.
References: <74v3ck$rui$1 AT oak DOT prod DOT itd DOT earthlink DOT net>
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Date: Sun, 13 Dec 1998 11:46:45 GMT
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To: djgpp AT delorie DOT com
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In article <74v3ck$rui$1 AT oak DOT prod DOT itd DOT earthlink DOT net>, "Philip Rama" <philip18 AT earthlink DOT net> wrote:
>Can someone please take a look at this? I have some code that I'm going to
>use for a simple "pong" game (my first game ever!!!) and wrote everything
>from scratch. I'm trying to get a red circle to bounce off the sides of the
>walls, but can't get it to work right.
>
>I wrote another function for a circle that you can move around with your
>arrow keys, and I want to make it so that whenever it reaches the left side
>and continues on... it'll go all the way to the right side. Like...
>if (x == 0)
>  x == 639;
>I did that with all the sides, but only the left and top sides work. I was
>pretty much messing around with this one, but I never got it to work.
>
>Thx...
>-Philip Rama
>
>

Hi Philip!

There are at least two obvious errors in your code:
: 
1.  In the moving_circle function you calculate 
        value = rand()%2;
This makes value take the value 0 or 1. It will NEVER be 3.

2. In the movable_circle function you have a series of if statements.
Just consider what will happen, when x==639 holds: you will set it to
0, which will cause the following if-statement to set it to 639 again.
Also I would not use x==639, but x>638 because depending on the value of 
speed it might never take the value 639, but perhaps 640 and you couldn't 
trap that value.
I suggest to place the x==? or better x>? statements within the if (key?) 
blocks.

Hope I could help,


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Manni Heumann
Bielefeld

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