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comp.lang.c++

what's this???

questions

11/8/2008 9:38:00 AM

Today when I build a program,the compiler tells me there is no
error,but when I run it ,it shows " 1.#INF00000",what's the
meaning??????The program is as follows:
#include<stdio.h>
int main()
{ int x,y;
int w=0;
long double z=0;

for(x=0;x<=10;x++)

{if(x==0)

{w=1;}

else

{for(y=1;y<=x;y++)

{w*=y;} }

z+=(float)1/w;}



printf("%.9Lf",z);


return 0;}
4 Answers

Rolf Magnus

11/8/2008 11:42:00 AM

0

questions wrote:

> Today when I build a program,the compiler tells me there is no
> error,but when I run it ,it shows " 1.#INF00000",what's the
> meaning??????

One question mark is enough. More makes the question just look silly.
The meaning is probably that you are dividing by zero.
The maximum value that w would reach probably a lot bigger than int
can handle on your platform.

Pawel Dziepak

11/8/2008 11:43:00 AM

0

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

questions wrote:
> Today when I build a program,the compiler tells me there is no
> error,but when I run it ,it shows " 1.#INF00000",what's the
> meaning??????The program is as follows:
> #include<stdio.h>
> int main()
> { int x,y;
> int w=0;
> long double z=0;
>
> for(x=0;x<=10;x++)
>
> {if(x==0)
>
> {w=1;}
>
> else
>
> {for(y=1;y<=x;y++)
>
> {w*=y;} }
>
> z+=(float)1/w;}
>
>
>
> printf("%.9Lf",z);
>
>
> return 0;}

It looks like "int" is too small to fit the value you assign to w. You
should check which type is sufficient (limits.h). According to C++
standard the largest integer type is unsigned long int and the largest
floating point type is long double. In fact, the second one was enough
to made this code working on my implementation.

I'd suggest you to format your code in an easier to read way.

Pawel Dziepak
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maverik

11/8/2008 11:46:00 AM

0

> #include<stdio.h>

> z+=(float)1/w;}

> printf("%.9Lf",z);

Should you post to the c.l.c instead of c.l.c++

> what's the meaning??????

Looks like w is overflowed. Use long types / float, double / ...

want.to.be.professer

11/8/2008 12:11:00 PM

0

On 11?8?, ??5?37?, questions <mengqidhu...@yahoo.cn> wrote:
> Today when I build a program,the compiler tells me there is no
> error,but when I run it ,it shows " 1.#INF00000",what's the
> meaning??????The program is as follows:
> #include<stdio.h>
> int main()
> { int x,y;
> int w=0;
> long double z=0;
>
> for(x=0;x<=10;x++)
>
> {if(x==0)
>
> {w=1;}
>
> else
>
> {for(y=1;y<=x;y++)
>
> {w*=y;} }
>
> z+=(float)1/w;}
>
> printf("%.9Lf",z);
>
> return 0;}

overflow!!!
You can see by this:

#include<stdio.h>
int main()
{
int x,y;
int w=0;
long double z=0;

for(x=0;x<=10;x++)
{
if(x==0)
{
w=1;
}
else
{
for(y=1;y<=x;y++)
{
w*=y;
}
}
printf( " w : %d \n", w );
z+=(float)1/w;
printf("%.9Lf\n",z);
}
printf("%.9Lf\n",z);
return 0;
}