Message-ID:	<34FCFD1C.74DA97E2@osu.edu>
Date:	Wed, 04 Mar 1998 02:05:00 -0500
From:	Jeff Farris <farris DOT 15 AT osu DOT edu>
MIME-Version:	1.0
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Floating Point Exceptions
References:	<34FCC703 DOT BF1C4286 AT osu DOT edu> <34FCCB93 DOT CD995F45 AT concentric DOT net>
NNTP-Posting-Host:	206.183.228.106
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

D. Huizenga wrote:
> Why don't you post some source code?  This will give us a better idea of
> what is wrong.
> --
> Dan Huizenga

Theres a fair bit of it, but heres the part that deals w/ the doubles:


// function traverses the roster and moves what needs moved
void UpdateActors (roster_t *r, BITMAP *bkGround, BITMAP *surface)
{
  actor_t *p_actor = r->p_first;
  int distmoved_x, distmoved_y;

  while(p_actor != NULL)
  {
    p_actor->timesincelastmove_x += 1.0 / TICS_PER_SEC;
    p_actor->timesincelastmove_y += 1.0 / TICS_PER_SEC;

    distmoved_x = (int)(p_actor->timesincelastmove_x * p_actor->vel.x);
    distmoved_y = (int)(p_actor->timesincelastmove_y * p_actor->vel.y);

    if( distmoved_x != 0 || distmoved_y != 0 )
    {
        // clear old sprite
        blit(bkGround,                  // source
             surface,                   // dest
             p_actor->pos.x,            // source_x
             p_actor->pos.y,            // source_y
             p_actor->pos.x,            // dest_x
             p_actor->pos.y,            // dest_y
             p_actor->p_sprite->w,
             p_actor->p_sprite->h);

        // move it & bounds checking
        p_actor->pos.x += distmoved_x;
        if (p_actor->pos.x > 320)
        {
          p_actor->pos.x = 320;
          p_actor->vel.x = - p_actor->vel.x;
        }
        if (p_actor->pos.x < 0)
        {
          p_actor->pos.x = 0;
          p_actor->vel.x = - p_actor->vel.x;
        }

        p_actor->pos.y += distmoved_y;
        if(p_actor->pos.y > 200)
        {
          p_actor->pos.y = 200;
          p_actor->vel.y = - p_actor->vel.y;
        }
        if (p_actor->pos.y < 0)
        {
          p_actor->pos.y = 0;
          p_actor->vel.y = - p_actor->vel.y;
        }

        // draw new sprite
        draw_sprite(surface, p_actor->p_sprite, p_actor->pos.x,
p_actor->pos.y);
    }

    if (distmoved_x != 0) p_actor->timesincelastmove_x = 0.0;
    if (distmoved_y != 0) p_actor->timesincelastmove_y = 0.0;

    p_actor = p_actor->p_next;
  }
  return;
}


Some background info, type roster_t is basically the head node in a
linked list of actor_t's.  timesincelastmove_x and .._y are members
(type double) of the actor_t struct that accumulate the time in seconds
since an actor's position changed on the screen.  This function is only
called when a timer has changed, which is 25 times per second right now.

Thx for any help!

Jeff Farris

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