C / C++ / MFC

Member 14968771 wrote:

RTFM is not an answer I am looking for...

Member 14968771 wrote:

If it returns "error" - how can I actually read it / get it in human / verbose format ?

/* Create a new socket of type TYPE in domain DOMAIN, using
   protocol PROTOCOL.  If PROTOCOL is zero, one is chosen automatically.
   Returns a file descriptor for the new socket, or -1 for errors.  */
extern int socket (int __domain, int __type, int __protocol) __THROW;

/* Create two new sockets, of type TYPE in domain DOMAIN and using
   protocol PROTOCOL, which are connected to each other, and put file
   descriptors for them in FDS[0] and FDS[1].  If PROTOCOL is zero,
   one will be chosen automatically.  Returns 0 on success, -1 for errors.  */
extern int socketpair (int __domain, int __type, int __protocol,
		       int __fds[2]) __THROW;

/* Give the socket FD the local address ADDR (which is LEN bytes long).  */
extern int bind (int __fd, __CONST_SOCKADDR_ARG __addr, socklen_t __len)
     __THROW;

/* Put the local address of FD into *ADDR and its length in *LEN.  */
extern int getsockname (int __fd, __SOCKADDR_ARG __addr,
			socklen_t *__restrict __len) __THROW;

AF_INET

AF_BLUETOOTH

k5054@localhost]$ cpp -include stdlib.h -dM /dev/null | grep -E 'define (THROW|LEAF)>'
#define __LEAF , __leaf
#define THROW __attribute ((nothrow __LEAF))
[k5054@localhost]$ 

#include <cerrno>
#include <cstring>

int ret = socket(foo, bar, baz); // socket() returns -1 on error and sets global var errno

if(ret == -1 ) {
   switch (errno) {
      case EACCES:
          // handle EACCES issue
          break;
      // etc.
      default:
          // print out the text associated with the error using strerror()
          std::cerr << "socket() returned error " << strerror(errno) << '\n';
     }
}

errno = 0;
ret = somefn(blah, blah, blah);
if (errno) {
    // do stuff
}

/* Find endpoint of line with given angle*/
void find_endpoint (double angle, int* x, int* y)
{
  assert (angle >= 0 && angle < 360);
  if (angle >= 315 || angle <= 45) //end point on right side
  {
    *x = LOCAL_MAP_NUM_X_CELLS;
    *y = (int)round((1 + sin (angle * DEG_TO_RAD)) * LOCAL_MAP_NUM_Y_CELLS / 2);
  }
  else if (angle <= 135) //endpoint on top side 
  {
    *y = LOCAL_MAP_NUM_Y_CELLS;
    *x = (int)round((1 + cos (angle * DEG_TO_RAD)) * LOCAL_MAP_NUM_X_CELLS / 2);
  }
  else if (angle < 225) //endpoint of left side
  {
    *x = 0;
    *y = (int)round((1 + sin (angle * DEG_TO_RAD)) * LOCAL_MAP_NUM_Y_CELLS / 2);
  }
  else //endpoint of bottom side
  {
    *y = 0;
    *x = (int)round((1 + cos (angle * DEG_TO_RAD)) * LOCAL_MAP_NUM_X_CELLS / 2);
  }
}

// a point in matrix
struct pt {
  int x;
  int y;
};

void bresenham (int x0, int y0, int x1, int y1, std::vector<pt>& cell)
{
  int dx = abs (x1 - x0);
  int sx = x0 < x1 ? 1 : -1;
  int dy = -abs (y1 - y0);
  int sy = y0 < y1 ? 1 : -1;
  int error = dx + dy;

  while (1)
  {
    cell.push_back ({ x0, y0 });
    if (x0 == x1 && y0 == y1)
      break;
    int e2 = 2 * error;
    if (e2 >= dy)
    {
      if (x0 == x1)
        break;
      error = error + dy;
      x0 = x0 + sx;
    }
    if (e2 <= dx)
    {
      if (y0 == y1)
        break;
      error = error + dx;
      y0 = y0 + sy;
    }
  }
}

int main (int argc, char **argv)
{
  int x1, y1;
  std::vector<pt> cells;

  //First quadrant, angle < 45
  find_endpoint (30., &x1, &y1);
  bresenham (100, 100, x1, y1, cells);
  cout << "Angle 30 degrees. End point: "<<x1 << ',' << y1 << endl;
  print_cells (cells);
  cout << endl;
//...

Gulshan Negi wrote:

performance in each language

• a blank then set was_blank = 1;
• not a blank then, depending on the was_blank flag increment the word count (or do nothing), eventually clear the flag: was_blank = 0;
  
  "In testa che avete, Signor di Ceprano?"
  -- Rigoletto

#include <stdargs>
void ProcessCommand (char* command, ...)
{
  va_list params; //opaque structure needed to process variable arguments lists

  va_start (params, command); //initialize with the last fixed argument before ellipsis

  // You need to know how many arguments to expect. Assume that args_count function tells you that
  // args_count is your function not some standard function
  int narg=args_count(command);
  for (i=0; i<narg; i++)
  {
    //Get next argument
    QString* pstr = va_arg (params, (QString*));

    // do something with the string
  }
  va_end(params); //cleanup

void ProcessCommand (char* command, int count, ...)

void ProcessCommand (char *command, std::vector<QString*> verify)
{
  for (auto& pstr : verify)
  {
    //do something with it
  }
}