Fix some issues that may cause floating point issues (#284)

Author: user202729

content/geometry/CirclePolygonIntersection.h

@@ -23,7 +23,7 @@ double circlePoly(P c, double r, vector<P> ps) {
 		if (det <= 0) return arg(p, q) * r2;
 		auto s = max(0., -a-sqrt(det)), t = min(1., -a+sqrt(det));
 		if (t < 0 || 1 <= s) return arg(p, q) * r2;
-		P u = p + d * s, v = p + d * t;
+		P u = p + d * s, v = q + d * (t-1);
 		return arg(p,u) * r2 + u.cross(v)/2 + arg(v,q) * r2;
 	};
 	auto sum = 0.0;

content/geometry/PolygonCut.h

@@ -27,10 +27,10 @@ vector<P> polygonCut(const vector<P>& poly, P s, P e) {
 	vector<P> res;
 	rep(i,0,sz(poly)) {
 		P cur = poly[i], prev = i ? poly[i-1] : poly.back();
-		bool side = s.cross(e, cur) < 0;
-		if (side != (s.cross(e, prev) < 0))
-			res.push_back(lineInter(s, e, cur, prev).second);
-		if (side)
+		auto a = s.cross(e, cur), b = s.cross(e, prev);
+		if ((a < 0) != (b < 0))
+			res.push_back(cur + (prev - cur) * (a / (a - b)));
+		if (a < 0)
 			res.push_back(cur);
 	}
 	return res;