From: "[taurus AT ptel DOT net]" <taurus AT ptel DOT dot DOT net>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Newbie Question : Polygon class
Date: Tue, 01 Jul 1997 10:44:28 -0500
Organization: MEANS
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Tan Mu Yen wrote:
> 
> I am trying to write a polygon class that allows me to add vertex to it
> using linked list ... ie I can add or delete a  vertex anytime using
> the polygon ...
> 
> Anyone has any idea? pls help me!
  I wouldn't try it if I were you, linked lists can be very useful, but
for storing vertexes (which need to be accessed often, and not always in
consecutive order) a simple array is much nicer.  If you need to add &
delete vertexes, just make the array large enough to hold the maximum
number of vertexes & keep a record of how many you actually are using:
typedef struct
{
 int num_verts;
 VERTEX verts[MAX_VERTS];
 .
 .
 .
} POLY;
To delete a vert 'v' just do:
 memcpy(ply->verts[v],ply->verts[v+1],ply->num_verts-v-1);
where ply = POLY*. (This is slower than a linked list, but not by much,
and you're not going to be deleting verts as often as you'll be using
them.)
  Just as a guess... You're trying to make an editor, aren't you?  If
that's the case and you'll not be modifying the polygons in the program
that finally uses them, just write and read num_verts vertexes from the
storage file, then you'll not be wasting memory or disk space.
  Hope this helps,

  Sincerely, 
    Joshua Heyer
    imwho AT hotmail DOT com

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