preciseness. lol

[Bleech]

hey all,
well I am trying to complete an assignment, and getting real close, but not close enough for my liking .

please take a look at the attached PDF, and then take a look at my program:

/* prog02assign.c */

#include <stdio.h>
/*#include <math.h>*/

int main(void)
{
	int i;
	float f;
	unsigned double p = 3.140000000, d2;

	printf("Please enter a decimal value between 1 and 100: ");
	scanf("%d", &d2);

	printf("\nVariable\t0 Decimals\t5 Decimals\t9 Decimals\n");

	i = 2 * p;

	printf("i (2*pi)\t%d\t\t%f\t%.9f\n", (int)i, (float)i, (float)i);

	f = 3 * p;

	printf("f (3*pi)\t%d\t\t%f\t%.9f\n", (int)f, f, f);

	d2 = d2 * p;

	printf("d2 (n*pi)\t%d\t\t%f\t%.9f\n\n\n", (int)d2, (float)d2, (float)d2);

	return 0;
}

when you enter 35.628 see how close my results are to the screenshot? close, but not close enough IMO. math.h is commented out because my MSVC++ 6.0's math.h does not appear to define a symbolic constant for pi.

note that I am declaring an unsigned double, which I don't think is right, the compiler is issuing a warning for it. but without d2 being unsigned, I get ugly signed results printed for d2.

could anyone please help me with making my output more precise here? any help is greatly appreciated, I know this program is ugly, but its the closest I can get to the screenshot.


thank you in advance!

[quzah]

Pi is not "3.1400000".
Floating point numbers are not accurate.
Put two and two together, and get 4.123235434563465345345.


Quzah.

[Bleech]

changing the value of p to something more precise like 3.141592653 (which is as precise as I can get) makes no difference on the output here, I suppose thats what you mean by floating point numbers are not accurate.

I am just curious as to why when I input 35.628 into my program I get 105 for d2 and in his screenshot he gets 111. thats quite a difference. I'm somewhat of a perfectionist, and this is bugging me, as you see I have the output formatted exactly as his .

[Salem]

> scanf("%d", &d2);
I'm surprised you get anything meaningful at all.
Input a double is "%lf", not "%d"

Also, all those (float) casts of doubles in printf are pointless, because it just converts them straight back into doubles (it's a variable argument).

[Bleech]

thank you very much Salem.

it is now outputting just as I wanted.