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

["Mike Main" <anime6@earthlink.net>]

You guys do know that the sin() functions is math.h only accept an angle in
radians right?  To convert a degree angle to radians just use this
conversion factor:

                               pi
(degrees)   X   ---------------
                         180 degrees

----- Original Message -----
From: "slick willy" <bporter@flashcom.net>
To: <gameprogrammer@gameprogrammer.com>
Sent: Tuesday, September 05, 2000 6:02 PM
Subject: Re: Some trig trouble -- and IEEE floating point format


> 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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