Hi,
I'm using a mingw64 port of gcc-4.7.0 on Windows Vista64:
#############################
C:\_32\C>x86_64-w64-mingw32-gcc -v
Using built-in specs.
COLLECT_GCC=x86_64-w64-mingw32-gcc
COLLECT_LTO_WRAPPER=c:/_64/alt/bin/../libexec/gcc/x86_64-w64-mingw32/4.7.0/lto-wrapper.exe
Target: x86_64-w64-mingw32
Configured with:
../../../build/gcc/src/configure --target=x86_64-w64-mingw32
--prefix=/c/bb/vista64-mingw32/mingw-x86-x86_64/build/build/root
--with-sysroot=/c/bb/vista64-mingw32/mingw-x86-x86_64/build/build/root
--enable-languages=all,obj-c++
--enable-fully-dynamic-string --disable-multilib
Thread model: win32
gcc version 4.7.0 20110410 (experimental) (GCC)
############################
I'm just starting to play with the _Decimal64 type.
First thing I'm wondering is how we reliably print out the _Decimal64 values
in our programs. Is there a formatter we can use with printf() ?
For the moment, I've simply been casting the _Decimal64 variable to a double
and formatting with %f:
printf("%f\n", (double)decimal64);
That's good enough to show me that I'm getting sane values - though I think
I ought to find out how to do it correctly.
I did, however, come across something that appears to me to be *not* so
sane:
############################
#include <stdio.h>
#include <stdlib.h>
int main(void) {
_Decimal64 inf_d64, nan_d64;
double inf_d, nan_d;
inf_d64 = 1.0DD/0.0DD;
inf_d = 1.0/0.0;
nan_d64 = inf_d64/inf_d64;
nan_d = inf_d/inf_d;
printf("%f %f\n", (double)nan_d64, nan_d);
nan_d64 = -nan_d64;
nan_d = -nan_d;
printf("%f %f\n", (double)nan_d64, nan_d);
return 0;
}
/**********************
Outputs:
1.#QNAN0 -1.#IND00
-1.#IND00 1.#QNAN0
Expected:
-1.#IND00 -1.#IND00
1.#QNAN0 1.#QNAN0
***********************/
############################
Whereas the "positive" nan is usually represented as -1.#IND00 and the
"negative" nan as 1.#QNAN0, the _Decimal64 nans are (it seems) being
represented the other way about.
Is this just a consequence of my improper way of printing those _Decimal64
values ?
What ought we see when we print a _Decimal64 nan on Windows?
Cheers,
Rob
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