mpq_get_d() rounding for different platforms?

[Sisyphus]

----- Original Message ----- 
From: "K Shen" <kishshen at yahoo.com>

> For example, for the rational 4/5,
>
> the MinGW version returns 0.79999999999999993, while the Linux version
> returns 0.80000000000000004.

Make sure that the assignment of 4/5 is being carried out in the same way.

As the following little program demonstrates, mpq_set_str(q, "4/5", 10) and 
mpq_set_d(q, (double) 4 / 5) assigm different values:

#############################
#include <stdio.h>
#include <gmp.h>

int main(void) {
    mpq_t q1;
    mpq_t q2;

    mpq_init(q1);
    mpq_init(q2);

    mpq_set_str(q1, "4/5", 10);
    mpq_set_d(q2, (double)4 / 5);

    printf("%.17f\n", mpq_get_d(q1));
    printf("%.17f\n", mpq_get_d(q2));

    mpq_clear(q1);
    mpq_clear(q2);
    return 0;
}
#############################

For me (both Linux and MinGW) that outputs:

0.79999999999999993
0.80000000000000004

Cheers,
Rob