Version 5.0 The LEDA User Manual

point p.reflect(const point& q, const point& r)
point p.reflect(const point& q)
returns p reflected across the straight line passing
through q and r.
returns p reflected across point q.
vector p − const point& q returns the difference vector of the coordinates.
Non-Member Functions
int cmp distances(const point& p1 , const point& p2 , const point& p3 ,
const point& p4 )
compares the distances (p1 , p2 ) and (p3 , p4 ). Returns
+1 (−1) if distance (p1 , p2 ) is larger (smaller) than distance
(p3 , p4 ), otherwise 0.
point center(const point& a, const point& b)
point midpoint(const point& a, const point& b)
returns the center of a and b, i.e. a + ⃗ ab/2.
returns the center of a and b.
int orientation(const point& a, const point& b, const point& c)
computes the orientation of points a, b, and c as the
sign of the determinant
∣
a x a y 1
b x b y 1
c x c y 1
∣
i.e., it returns +1 if point c lies left of the directed line
through a and b, 0 if a,b, and c are collinear, and −1
otherwise.
int cmp signed dist(const point& a, const point& b, const point& c,
const point& d)
compares (signed) distances of c and d to the straight
line passing through a and b (directed from a to b). Returns
+1 (−1) if c has larger (smaller) distance than d
and 0 if distances are equal.
double area(const point& a, const point& b, const point& c)
computes the signed area of the triangle determined by
a,b,c, positive if orientation(a, b, c) > 0 and negative
otherwise.