Re: Some trig trouble -- and IEEE floating point format

[Lionel Pinkhard <lionelp@worldonline.co.za>]

Hi,

Well, angle_deg was set to 60.0, but I solved the problem, I don't know
how, but I just recompiled the code and it worked. But I tried using that
sind() function, and I couldn't get it working, which header file needs to
be included?

And what exactly is a 'cast'?

One more thing: Does somebody know of a simple method (under Dos) to input
from the keyboard? Except using a kbhit()/getch() combo, since that seems
to be too slow in my situation. Is it possible to input directly from port
0x60? And manually clear the buffer, etc. (Well, I'm pretty sure it's
possible, 'cause Dos can do it :-) ) If so, how?

Ciao,

Lionel

P.s. Does anybody know of any source code for a mouse driver? I'm working
on an operating system, and I would really like to add some mouse support.

On Tue, 5 Sep 2000, slick willy wrote:

> unless your angle_deg is not a double, then i dont see a problem with the
> code. however, you could always try sind(double x) or sindf(float x) which
> both take an angle in degrees as their argument.
> 
> --Bill
> 
> ----- Original Message -----
> From: "Lionel Pinkhard" <lionelp@worldonline.co.za>
> To: <gameprogrammer@gameprogrammer.com>
> Sent: Tuesday, September 05, 2000 3:31 PM
> Subject: Some trig trouble -- and IEEE floating point format
> 
> 
> > Hey guys/gals,
> >
> > I got some trouble with a simple procedure to convert degrees into
> > radians, and then calculate the sine of the angle, here's my code (with a
> > 'printf' for diagnostics -- value is in angle_deg):
> >
> > double angle_rad, sine;
> >
> > angle_rad = angle_deg * M_PI / 180.0;
> > sine = sin(angle_rad);
> >
> > printf("The sine of %.2f is %.8f.\r\n", angle_deg, sine);
> >
> > If I try to run this code, I get "Floating point error: Domain.",
> > "Abnormal program termination". What am I doing wrong? I have an idea it's
> > something really simple.
> >
> > Next, a little problem with pointers:
> >
> > I'm using pointers to return the movement from the joystick:
> >
> > Function:
> > void joy_movement(signed char *x, signed char *y) {
> >     unsigned short absx, absy;
> >     signed char deltax, deltay;
> >
> >     joy_absolute(&absx, &absy);
> >
> >     << rest of code here >>
> >
> >     *x = deltax;
> >     *y = deltay;
> > }
> >
> > Program:
> >     joy_movement(&x, &y);
> >
> > joy_movement is a function to get the movement from the joystick in the
> > range -127 to 128 (that's why I'm using a char). joy_absolute is a
> > function to return the axises of the joystick, and is in the same format
> > as joy_movement. When I compile I get the 'unportable pointer' messages,
> > and the functions don't work.
> >
> > Hope somebody can help me out here!
> >
> > Nextly, somebody asked about floating point numbers, well for
> > single-precision (4 bytes), the sign takes 1 bit, the exponent takes 8
> bits and
> > the mantissa uses the other 23 bits (the number is 32-bit). For
> > double-precision (8 bytes), the sign takes 1 bit, the exponent takes 11
> > bits and the mantissa uses the other 52 bits (the number is 64-bit). I'm
> > not sure about how correct this is, but try printing out a float in
> > hexadecimal or something (I'm not sure whether that is possible, can
> > somebody help me out there?) Anyways, this is the IEEE format, there are
> > also other formats, such as Microsoft's format, but I think that's
> > obsolete by now.
> >
> > Ciao,
> >
> > Lionel
> >
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