incorrect printf o/p for doubles

[Yogesh Khanolkar]

Hi,

I am getting incorrect o/p from the code below:

#include<stdio. h>
#include<float. h>
#include<limits .h>
main()
{
double val,val1;
val=12345678901 2.123456;
val1=1234567890 12.123456;
val2=val*val1;
printf("%f\n",v al2);
}

The result I get is 152415787531839 67100000.000000 instead of the correct value.

I am running on HP-UX 11 with ansi c compiler.

Can anyone let me know why I am getting this result.

[James Hu]

Keith Thompson <ks*@cts.com> wrote in message news:<lz******* *****@cts.com>. ..

James Hu <jx*@despammed. com> writes:

On 2003-10-30, Yogesh Khanolkar <yo************ **@azuresolutio ns.com> wrote:

{
double val,val1;
val=12345678901 2.123456;
val1=1234567890 12.123456;
val2=val*val1;

It looks like val2 is defaulting to an int type, and you are trying to
print it out like a double.

Undeclared variables don't default to int. Some compilers, especially
old ones, might let you get away with

val2;

as a declaration for val2 with a default type of int, but it's never
been possible to omit the declaration altogether.

Crikes! Thanks for the correction.

-- James

[Jarno A Wuolijoki]

On Fri, 31 Oct 2003, Keith Thompson wrote:

Undeclared variables don't default to int. Some compilers, especially
old ones, might let you get away with

val2;

as a declaration for val2 with a default type of int, but it's never
been possible to omit the declaration altogether.

Never in standard C at least, but where does this odd interpretation
come from then? Did K&R allow it or is it just some awfully widespread
hack?

[James Hu]

On 2003-11-01, Jarno A Wuolijoki <jw******@cs.He lsinki.FI> wrote:

On Fri, 31 Oct 2003, Keith Thompson wrote:

Undeclared variables don't default to int. Some compilers, especially
old ones, might let you get away with

val2;

as a declaration for val2 with a default type of int, but it's never
been possible to omit the declaration altogether.

Never in standard C at least, but where does this odd interpretation
come from then? Did K&R allow it or is it just some awfully widespread
hack?

Many pre-ANSI C compilers supported a syntax along the lines of:

var;

to declare a global integer variable. It also supported a syntax of

foo(var)
var; /* this line is optional */
{
/* ... */
}

to declare an integer parameter. (As an aside, gcc still accepts
the above syntax.)

I incorrectly assumed pre-ANSI C compilers allowed the implicit
declaration of an integer variable, similar to the way pre-ANSI C
and C90 do for a function returning int.

-- James

[Dan Pop]

In <lz************ @cts.com> Keith Thompson <ks*@cts.com> writes:

James Hu <jx*@despammed. com> writes:

On 2003-10-30, Yogesh Khanolkar <yo************ **@azuresolutio ns.com> wrote:

>
> #include<stdio. h>
> #include<float. h>
> #include<limits .h>
> main()
> {
> double val,val1;
> val=12345678901 2.123456;
> val1=1234567890 12.123456;
> val2=val*val1;
> printf("%f\n",v al2);
> }
>

It looks like val2 is defaulting to an int type, and you are trying to
print it out like a double.

Undeclared variables don't default to int. Some compilers, especially
old ones, might let you get away with

val2;

as a declaration for val2 with a default type of int, but it's never
been possible to omit the declaration altogether.

And that is/was allowed at file scope only, because at block scope this
looks like an expression statement with an undeclared identifier.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de