// define function pointer type
typedef double (*FUNC_POINTER)(double);
  
// define callback function
double func(double a)
{
	return a*2;
}

// function pointer as parameter
double FuncCall(FUNC_POINTER myfunc, double a)  
{
	return myfunc(a) + 1;  // using function pointer
}

// testing function
void testFuncCall()
{	
	double dd = FuncCall(func, 1);  // pass a function as parameter
	out_double("", dd); // shoule output 3
}