"long double" and "printf"


Z

Zero

Hi everybody,

i want to write a small program, which shows me the biggest and
smallest number in dependance of the data type.

For int the command could be:

printf("\n%20s\t%7u\t%13i\t%13i","signed int",sizeof(signed
int),INT_MIN,INT_MAX);

But what do I have to do when I want to print out the numbers of data
type "long double".

I tried
printf("\n%20s\t%7u\t%13Lf\t%13Lf","long double",sizeof(long
double),LDBL_MIN,LDBL_MAX);
but this results in

long double 12 0.000000 -1.#QNAN0

Does anybody has a solution.

I tried this with Bloodshed using the gnu-compiler.

Thanks for your help!
 
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P

pete

Zero said:
Hi everybody,

i want to write a small program, which shows me the biggest and
smallest number in dependance of the data type.

For int the command could be:

printf("\n%20s\t%7u\t%13i\t%13i","signed int",sizeof(signed
int),INT_MIN,INT_MAX);

But what do I have to do when I want to print out the numbers of data
type "long double".

I tried
printf("\n%20s\t%7u\t%13Lf\t%13Lf","long double",sizeof(long
double),LDBL_MIN,LDBL_MAX);
but this results in

long double 12 0.000000 -1.#QNAN0

Does anybody has a solution.

I tried this with Bloodshed using the gnu-compiler.

For something like that,
you should try to post a complete program.

/* BEGIN new.c */

#include <stdio.h>
#include <float.h>

int main(void)
{
printf("%s\n%u\n%Le\n%Le\n",
"long double",
(unsigned)sizeof(long double),
LDBL_MIN,
LDBL_MAX);
return 0;
}

/* END new.c */
 
Z

Zero

pete said:
For something like that,
you should try to post a complete program.

/* BEGIN new.c */

#include <stdio.h>
#include <float.h>

int main(void)
{
printf("%s\n%u\n%Le\n%Le\n",
"long double",
(unsigned)sizeof(long double),
LDBL_MIN,
LDBL_MAX);
return 0;
}

/* END new.c */

Thanks for your help. But i still get this message:

long double
12
0.000000e+000
-1.#QNAN0e+000

??
 
R

Richard Bos

Zero said:
But what do I have to do when I want to print out the numbers of data
type "long double".

I tried
printf("\n%20s\t%7u\t%13Lf\t%13Lf","long double",sizeof(long
double),LDBL_MIN,LDBL_MAX);
but this results in

long double 12 0.000000 -1.#QNAN0

Does anybody has a solution.

I tried this with Bloodshed using the gnu-compiler.

AFAICT this is a bug in Dev-C++. Their library and their headers don't
match on this detail. One (IIRC the header) thinks long doubles are
larger than doubles, the other (IIRC the printf() code) thinks they're
as large as doubles.

Richard
 
D

Dik T. Winter

> Thanks for your help. But i still get this message:
>
> long double
> 12
> 0.000000e+000
> -1.#QNAN0e+000

Some older compilers did use 'll' in stead of 'L' for long double.
 
Z

Zero

Zero said:
Hi everybody,

i want to write a small program, which shows me the biggest and
smallest number in dependance of the data type.

For int the command could be:

printf("\n%20s\t%7u\t%13i\t%13i","signed int",sizeof(signed
int),INT_MIN,INT_MAX);

But what do I have to do when I want to print out the numbers of data
type "long double".

I tried
printf("\n%20s\t%7u\t%13Lf\t%13Lf","long double",sizeof(long
double),LDBL_MIN,LDBL_MAX);
but this results in

long double 12 0.000000 -1.#QNAN0

Does anybody has a solution.

I tried this with Bloodshed using the gnu-compiler.

Thanks for your help!

I just tried the code with Visual C++ and there it seems
that there is no difference between double and long double?

Bloodshed says long double consists of 12 Bytes, Visual C++ says 12.
What is right now?
 
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Z

Zero

Zero said:
Hi everybody,

i want to write a small program, which shows me the biggest and
smallest number in dependance of the data type.

For int the command could be:

printf("\n%20s\t%7u\t%13i\t%13i","signed int",sizeof(signed
int),INT_MIN,INT_MAX);

But what do I have to do when I want to print out the numbers of data
type "long double".

I tried
printf("\n%20s\t%7u\t%13Lf\t%13Lf","long double",sizeof(long
double),LDBL_MIN,LDBL_MAX);
but this results in

long double 12 0.000000 -1.#QNAN0

Does anybody has a solution.

I tried this with Bloodshed using the gnu-compiler.

Thanks for your help!

I just tried the code with Visual C++ and there it seems
that there is no difference between double and long double?

Bloodshed says long double consists of 12 Bytes, Visual C++ says 8.
What is right now?
 
Z

Zero

Richard said:
AFAICT this is a bug in Dev-C++. Their library and their headers don't
match on this detail. One (IIRC the header) thinks long doubles are
larger than doubles, the other (IIRC the printf() code) thinks they're
as large as doubles.

Richard

How do you know that this is a bug? Is there a side, where this
information can be fetched?
 
F

Flash Gordon

Zero wrote:

I just tried the code with Visual C++ and there it seems
that there is no difference between double and long double?

Bloodshed says long double consists of 12 Bytes, Visual C++ says 8.
What is right now?

Both. The C standard does not mandate exact sizes only minimums.
 
T

Tim Prince

Flash said:
Zero wrote:



Both. The C standard does not mandate exact sizes only minimums.
Besides, the amount of unused storage doesn't directly answer your
problem. Few of us would know whether specifying Bloodshed implies a
specific version of gcc and run-time library. Run-time libraries
associated with Windows versions of gcc which I have used didn't
implement 10-byte long double in printf(), even though it might be
supported in terms of basic operators. If it uses Visual C++ printf(),
evidently there will be no support for more than 8-byte data type.
 
D

Dann Corbit

Dik T. Winter said:
Some older compilers did use 'll' in stead of 'L' for long double.

I guess that he is using the GCC MINGW compiler which creates 80 bit
hardware long doubles, but which the Microsoft runtime libraries do not
match (for MS VC++ double and long double are the same type).
 
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J

jacob navia

pete a écrit :
For something like that,
you should try to post a complete program.

/* BEGIN new.c */

#include <stdio.h>
#include <float.h>

int main(void)
{
printf("%s\n%u\n%Le\n%Le\n",
"long double",
(unsigned)sizeof(long double),
LDBL_MIN,
LDBL_MAX);
return 0;
}

/* END new.c */


This produces:
long double
12
3.362103e-4932
1.189731e+4932

with lcc-win32
 
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R

Richard Bos

Zero said:
How do you know that this is a bug?

For starters, because the behaviour you observe is not correct. There
was a c.l.c thread on this very problem some time ago; if you search for
it I'm sure you can find it. In that thread, some people (including me)
did some experiments and concluded that it had to be a mismatch
somewhere in Dev-C++.

Richard
 

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