C / C++ / MFC

ON_UPDATE_COMMAND_UI(ID_MYMENUCOMMAND, OnUpdateMyMenu)<br />
(and)<br />
void CMainFrame::OnUpdateMyMenu(CCmdUI* pCmdUI)<br />
{<br />
pCmdUI->Enable(FALSE); // disable the menu item<br />
}<br />

class CSharableObject
{
public:
   CSharableObject( const TCHAR * p_pszName ) :
      c_hMutex( NULL )
   {
      c_hMutex = OpenMutex( SYNCHRONIZE, FALSE, p_pszName );
      if( c_hMutex == NULL )
      {
         c_hMutex = CreateMutex( NULL, FALSE, p_pszName );
         if( c_hMutex == NULL )
         {
            // Handle the error somehow...
         }
      }
   }

   ~CSharableObject()
   {
      if( c_hMutex != NULL )
      {
         CloseHandle( c_hMutex );
         c_hMutex = NULL;
      }
   }

   bool IsLocked()
   {
      // Test if some other thread has the mutex already...
      DWORD a_dwReason = WaitForSingleObject( c_hMutex, 0 );
      if( a_dwReason == WAIT_TIMEOUT )
         return true;
      return false;
   }

   unsigned long Lock( unsigned long p_ulTimeout = INFINITE )
   {
      // Wait for another thread to give up the mutex.
      return WaitForSingleObject( c_hMutex, p_ulTimeout );
   }

   bool Unlock()
   {
      // Give up the mutex.
      return ReleaseMutex( c_hMutex ) != 0;
   }

protected:
   HANDLE c_hMutex;
};

CSharableObject a_oLocker( _T("SomeUniqueName") );
 
// Lock the object.
a_oLocker.Lock();
 
// ... use the precious resource here...
 
// And when we are done we unlock it.
a_oLocker.Unlock();
 
// OR
if( !a_oLocker.IsLocked() )
{
   // Take one course of action.
}
else
{
   // Take another course of action.
}

int scale = 1000;

f*=scale;
if(f>0)
   f+=0.5;
else
   f-=0.5;
double d =(double)(((double)(int)f) / scale);

double round(double value, unsigned decimalPlaces)
{
	double scale = pow(10.0, (double)decimalPlaces);
	double temp = value * scale;
 
	temp += (value < 0 ? -0.5 : 0.5);
	return (int)temp / scale;
}

float fData = 2.7f;

float x = whatever;
long y = *(long*)(&x);
const __int64 signBit = (y & 0x80000000) << 32;
const __int64 exponent = (__int64( ((y >> 23)&0xff) - 127 + 1023)) << 52;
const __int64 fraction = (__int64(y & 0x007fffff)) << 29;
__int64 ly = signBit | exponent | fraction;
double lx = *(double*)(&ly);

<br />
float flt = 2.7f;<br />
TCHAR sz[65] = _T("");<br />
_stprintf(sz, _T("%.3f"), flt); // suppose you want 3 decimal accuracy<br />
<br />
// now value of sz must be _T("2.700"), convert it into a double<br />
double dbl = _tcstod(sz, NULL);<br />