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

["slick willy" <bporter@flashcom.net>]

sind() is in <math.h>
the man page for sind on my school's unix server says 'named in accordance
with the conventions specified in the "Future Library Directions" section of
the ANSI C standard.'
and its dated 1997, so i would assume its a standard function of the math
lib, but that might be a dangerous assumption.

as far as typecasting goes...think of it like this: if you try to give
someone a pile of crap (literally), you have no chance in hell at getting
rid of it. but put that crap in a green bag and call it 'fertilizer', people
will be more than happy to take it off your hands. get it? nomen est omen.

--Bill

----- Original Message -----
From: "Lionel Pinkhard" <lionelp@worldonline.co.za>
To: <gameprogrammer@gameprogrammer.com>
Sent: Tuesday, September 05, 2000 9:43 PM
Subject: Re: Some trig trouble -- and IEEE floating point format


> 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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