fix compilation on mac

wowViewerLib/src/engine/algorithms/grahamScan.cpp

@@ -3,14 +3,9 @@
 #include <algorithm>
 using namespace std;
 
-// Point having the least y coordinate, used for sorting other points
-// according to polar angle about this point
-//Point pivot;
-Point p0;
-
 // returns -1 if a -> b -> c forms a counter-clockwise turn,
 // +1 for a clockwise turn, 0 if they are collinear
-int ccw(Point a, Point b, Point c) {
+int ccw(const Point &a, const Point &b, const Point &c) {
     float area = (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
     if (area > 0)
         return -1;
@@ -20,7 +15,7 @@ int ccw(Point a, Point b, Point c) {
 }
 
 // returns square of Euclidean distance between two points
-float sqrDist(Point a, Point b)  {
+float sqrDist(const Point &a, const Point &b)  {
     float dx = a.x - b.x, dy = a.y - b.y;
     return dx * dx + dy * dy;
 }
@@ -43,7 +38,7 @@ void swap(Point &p1, Point &p2)
 
 // A utility function to return square of distance
 // between p1 and p2
-int distSq(Point &p1, Point &p2)
+int distSq(const Point &p1, const Point &p2)
 {
     return (p1.x - p2.x)*(p1.x - p2.x) +
            (p1.y - p2.y)*(p1.y - p2.y);
@@ -54,7 +49,7 @@ int distSq(Point &p1, Point &p2)
 // 0 --> p, q and r are colinear
 // 1 --> Clockwise
 // 2 --> Counterclockwise
-int orientation(Point &p, Point &q, Point &r)
+int orientation(const Point &p, const Point &q, const Point &r)
 {
     int val = (q.y - p.y) * (r.x - q.x) -
               (q.x - p.x) * (r.y - q.y);
@@ -63,21 +58,6 @@ int orientation(Point &p, Point &q, Point &r)
     return (val > 0)? 1: 2; // clock or counterclock wise
 }
 
-// A function used by library function qsort() to sort an array of
-// points with respect to the first point
-int compare(const void *vp1, const void *vp2)
-{
-    Point *p1 = (Point *)vp1;
-    Point *p2 = (Point *)vp2;
-
-    // Find orientation
-    int o = orientation(p0, *p1, *p2);
-    if (o == 0)
-        return (distSq(p0, *p2) >= distSq(p0, *p1))? -1 : 1;
-
-    return (o == 2)? -1: 1;
-}
-
 Point nextToTop(stack<Point> &S)
 {
     Point p = S.top();
@@ -107,12 +87,23 @@ stack<Point> grahamScan(std::vector<Point> &points)    {
     // Place the bottom-most point at first position
     swap(points[0], points[min]);
 
+    // Point having the least y coordinate, used for sorting other points
+    // according to polar angle about this point
+    Point p0 = points[0];
+
     // Sort n-1 points with respect to the first point.
     // A point p1 comes before p2 in sorted ouput if p2
     // has larger polar angle (in counterclockwise
     // direction) than p1
-    p0 = points[0];
-    qsort(&points[1], n-1, sizeof(Point), compare);
+
+    std::sort(points.begin()+1, points.end(), [&p0](auto const &p1, auto const &p2) -> int {
+        // Find orientation
+        int o = orientation(p0, p1, p2);
+        if (o == 0)
+            return (distSq(p0, p2) >= distSq(p0, p1))? -1 : 1;
+
+        return (o == 2)? -1: 1;
+    });
 
     // If two or more points make same angle with p0,
     // Remove all but the one that is farthest from p0