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#include <fenv.h>
#include <iostream>
#include <limits>
int modes[4] = { FE_TOWARDZERO, FE_UPWARD, FE_DOWNWARD, FE_TONEAREST };
std::string str (int mode)
{
switch (mode)
{
case FE_TOWARDZERO: return "FE_TOWARDZERO";
case FE_UPWARD: return "FE_UPWARD";
case FE_DOWNWARD: return "FE_DOWNWARD";
case FE_TONEAREST: return "FE_TONEAREST";
default: throw __LINE__;
}
}
int fetestround ()
{
volatile double eps = std::numeric_limits<double>::denorm_min();
double x = -1.0;
double y = 1.0;
volatile double x_plus_eps = x + eps;
volatile double y_minus_eps = y - eps;
if ((x == x_plus_eps) && (y == y_minus_eps))
return FE_TONEAREST;
if (y == y_minus_eps)
return FE_UPWARD;
if (x == x_plus_eps)
return FE_DOWNWARD;
return FE_TOWARDZERO;
}
int main (int argc, char* argv[])
{
int errors = 0;
int mode_get = fegetround();
std::cout << "fegetround() = " << str(mode_get) << " " << std::endl;
for (int i=0; i<4; i++)
{
int mode_set = modes[i];
fesetround (mode_set);
std::cout << "fesetround (" << str(mode_set) << ")" << std::endl;
int mode_get = fegetround();
std::cout << "fegetround() = " << str(mode_get) << " ";
bool ok_get = mode_get == mode_set;
if (!ok_get)
errors++;
std::cout << (ok_get ? "(ok)" : "(error)") << std::endl;
int mode_test = fetestround();
std::cout << "fetestround() = " << str(mode_test) << " ";
bool ok_test = mode_test == mode_set;
if (!ok_test)
errors++;
std::cout << (ok_test ? "(ok)" : "(error)") << std::endl;
}
return errors;
}
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