Roberto Bagnara wrote:
Hi there,
the following little program
#include <stdio.h>
int main() {
double d;
scanf("%lf", &d);
printf("%.1000g\n", d);
return 0;
}
does this on Linux/i686
$ gcc -W -Wall in.c
$ a.out
70.9
70.900000000000005684341886080801486968994140625
and does the following under Cygwin on the same machine:
[EMAIL PROTECTED] /tmp
$ gcc -W -Wall in.c
[EMAIL PROTECTED] /tmp
$ ./a.exe
70.9
70.90000000000000568434188608080148696899414
Why? Is there a way to reconcile the two behaviors?
Notice that I know about the x87 and its vaguaries:
nonetheless I wonder why such a scanf immediately
followed by a printf shows a difference between
Cygwin and Linux.
If you haven't gone out of your way to install similar printf() support
libraries on cygwin and linux, they will definitely not be the same. My
past reading of various relevant documents convinced me that digits
beyond the 17th in formatting of doubles are not required by any
standard to be consistent between implementations. They have no useful
function, as 17 digits are sufficient to determine uniquely the
corresponding binary value in IEEE 754 format.
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