C / C++ / MFC

Member 14968771 wrote:

..RTFM.. everybody knows that..." disease.

Francis Lagar wrote:

How can you insert th

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 ?

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;
//...