How to get more precision in C ?

[pereges]

I would like to have precision upto atleast 8 digits in my numerical
computation program. I have tried using doubles but I keep getting
results only till 6 places after decimal. eg.

#include <stdio.h>
#define M_PI 3.1415926535897 9323846 /* M_PI is not defined in math.h
according to my compiler*/

int main(void)
{
double s;
s = M_PI;
printf("%f", s);
return 0;

}

[Gordon Burditt]

>I would like to have precision upto atleast 8 digits in my numerical

>computation program. I have tried using doubles but I keep getting
results only till 6 places after decimal. eg.

You only *print* 6 digits after the decimal. You may be getting greater
precision in the actual computation.

Try: printf("%300.20 0f", s);
although this is primarily useful for debugging. A double won't
have nearly this many digits of precision.

>#include <stdio.h>
#define M_PI 3.1415926535897 9323846 /* M_PI is not defined in math.h
according to my compiler*/

int main(void)
{
double s;
s = M_PI;
printf("%f", s);
return 0;

}

[Walter Roberson]

In article <bd************ *************** *******@q27g200 0prf.googlegrou ps.com>,
pereges <Br*****@gmail. comwrote:

>I would like to have precision upto atleast 8 digits in my numerical
computation program. I have tried using doubles but I keep getting
results only till 6 places after decimal. eg.

>#include <stdio.h>
#define M_PI 3.1415926535897 9323846 /* M_PI is not defined in math.h
according to my compiler*/

>int main(void)
{
double s;
s = M_PI;
printf("%f", s);
return 0;
}

Specify a precision with your %f format, such as %.60f . The default
for %f is 6.

Also, to be safe, ensure your output ends in a newline. For example,

printf("%.9f\n" , s);

--
Q: Why did the chicken cross the Mobius strip?

A: There were manifold reasons.

[user923005]

On Apr 10, 8:53*pm, pereges <Brol...@gmail. comwrote:

I would like to have precision upto atleast 8 digits in my numerical
computation program. I have tried using doubles but I keep getting
results only till 6 places after decimal. eg.

#include <stdio.h>
#define M_PI 3.1415926535897 9323846 /* M_PI is not defined in math.h
according to my compiler*/

int main(void)
{
* * * * double s;
* * * * s = M_PI;
* * * * printf("%f", s);

return 0;

}

Try it this way:

#include <stdio.h>
#include <float.h>
static const double pi_approximatio n =
3.1415926535897 932384626433832 795;

int main(void) {
printf("My pi approximation is %.*g\n", DBL_DIG + 1,
pi_approximatio n);
return 0;
}

[pereges]

On Apr 11, 11:10 am, user923005 <dcor...@connx. comwrote:

On Apr 10, 8:53 pm, pereges <Brol...@gmail. comwrote:

I would like to have precision upto atleast 8 digits in my numerical
computation program. I have tried using doubles but I keep getting
results only till 6 places after decimal. eg.

#include <stdio.h>
#define M_PI 3.1415926535897 9323846 /* M_PI is not defined in math.h
according to my compiler*/

int main(void)
{
double s;
s = M_PI;
printf("%f", s);

return 0;

}

Try it this way:

#include <stdio.h>
#include <float.h>
static const double pi_approximatio n =
3.1415926535897 932384626433832 795;

int main(void) {
printf("My pi approximation is %.*g\n", DBL_DIG + 1,
pi_approximatio n);
return 0;

}

why declare pi_approximatio n as a static const ?

[Richard Heathfield]

pereges said:

<snip>

why declare pi_approximatio n as a static const ?

Were you planning on changing it?
--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[pereges]

On Apr 11, 12:05 pm, Richard Heathfield <[e-mail].i nvalidwrote:

pereges said:

<snip>

why declare pi_approximatio n as a static const ?

Were you planning on changing it?

if you are not planning to change it, then declare it as const. what
is the purpose behind declaring it as static ?

[pereges]

On Apr 11, 12:05 pm, Richard Heathfield <[e-mail].i nvalidwrote:

pereges said:

<snip>

why declare pi_approximatio n as a static const ?

Were you planning on changing it?

if you are not planning to change it, then declare it as const. what
is the purpose behind declaring it as static ?

[Richard Heathfield]

pereges said:

On Apr 11, 12:05 pm, Richard Heathfield <[e-mail].i nvalidwrote:

>pereges said:

<snip>

why declare pi_approximatio n as a static const ?

Were you planning on changing it?

if you are not planning to change it, then declare it as const. what
is the purpose behind declaring it as static ?

I would imagine that Dann did that to avoid the possibility of a name clash
with other file scope objects, either in other translation units or
perhaps in a third-party library. It wouldn't really matter in a toy
program like this, of course.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Philip Potter]

pereges wrote:

On Apr 11, 11:10 am, user923005 <dcor...@connx. comwrote:

>On Apr 10, 8:53 pm, pereges <Brol...@gmail. comwrote:

>>#define M_PI 3.1415926535897 9323846 /* M_PI is not defined in math.h

static const double pi_approximatio n =
3.141592653589 793238462643383 2795;

why declare pi_approximatio n as a static const ?

#defines and consts are different beasts which can often serve a similar
purpose. Each has their own advantages and disadvantages - for example,
consts will do type-checking, while #defined constants can be used in
array dimensions (without creating a VLA).

There's a much more rigorous discussion of the differences between
#define and const here:

http://c-faq.com/cpp/constdefine2.html