#include <iostream>
#include <cstdio>
#include <cmath>
#include <cfenv>

using namespace std;

void
printme (const char *fmt, float f)
{
  union
  {
    float f;
    int i;
  } cvt;

  cvt.f = f;

  printf (fmt, f, cvt.i);
}

int
main (void)
{
  int rnd_mode;
  float fzero;
  float fpi;
  float falmostpi = 3.1415924;
  float fatan2, fasin;
  float fdiff;

  cout << "Please enter '0.0' and hit <Return> " << endl;
  cin >> fzero;
  cout << "--------------------" << endl;

  rnd_mode = fegetround();
  cout << "Default round mode is " << rnd_mode << endl;
  fesetround(FE_TOWARDZERO);
  rnd_mode = fegetround();
  cout << "TOWARDZERO round mode is " << rnd_mode << endl;
  fesetround(FE_TONEAREST);
  rnd_mode = fegetround();
  cout << "TONEAREST round mode is " << rnd_mode << endl;
  cout << "--------------------" << endl;

  printme ("TONEAREST : (float) almostpi = %.7f (0x%08x)\n", float (falmostpi + fzero));
  printme ("TONEAREST : (float) M_PI = %.7f (0x%08x)\n", float (M_PI + fzero));
  fesetround(FE_TOWARDZERO);
  printme ("TOWARDZERO: (float) M_PI = %.7f (0x%08x)\n", float (M_PI + fzero));
  printme ("TOWARDZERO: (float) almostpi = %.7f (0x%08x)\n", float (falmostpi + fzero));
  cout << "--------------------" << endl;

  cout << "Computed with TONEAREST" << endl;
  fesetround(FE_TONEAREST);
  fpi = float (M_PI + fzero);
  fatan2 = atan2f (fzero, float (fzero - 1));
  fdiff = fatan2 - fpi;
  printme ("atan2f (0.0f, -1.0f) = %.8f (0x%08x)\n", fatan2);
  printme ("atan2f (0.0f, -1.0f) - (float) M_PI = %.8f (0x%08x)\n", fdiff);
  fasin = 2.0f * asinf (float (1.0f + fzero));
  fdiff = fasin - fpi;
  printme ("2*asinf (1.0f) = %.8f (0x%08x)\n", fasin);
  printme ("2*asinf (0.0f, -1.0f) - (float) M_PI = %.8f (0x%08x)\n", fdiff);
  cout << "--------------------" << endl;

  cout << "Computed with TOWARDZERO" << endl;
  fesetround(FE_TOWARDZERO);
  fpi = float (M_PI + fzero);
  fatan2 = atan2f (fzero, float (fzero - 1));
  fdiff = fatan2 - fpi;
  printme ("atan2f (0.0f, -1.0f) = %.8f (0x%08x)\n", fatan2);
  printme ("atan2f (0.0f, -1.0f) - (float) M_PI = %.8f (0x%08x)\n", fdiff);
  fasin = 2.0f * asinf (float (1.0f + fzero));
  fdiff = fasin - fpi;
  printme ("2*asinf (1.0f) = %.8f (0x%08x)\n", fasin);
  printme ("2*asinf (0.0f, -1.0f) - (float) M_PI = %.8f (0x%08x)\n", fdiff);
  cout << "--------------------" << endl;

  return 0;
}