1 files changed, 37 insertions, 0 deletions
diff --git a/geometry/lines.cpp b/geometry/lines.cpp
new file mode 100644
index 0000000..ec6fdde
--- /dev/null
+++ b/geometry/lines.cpp
@@ -0,0 +1,37 @@
+struct pt { //complex<double> does not work here, becuase we need to set pt.x and pt.y
+	double x, y;
+	pt() {};
+	pt(double x, double y) : x(x), y(y) {};
+};
+
+struct line {
+	double a, b, c; //a*x+b*y+c, b=0 <=> vertical line, b=1 <=> otherwise
+};
+
+line pointsToLine(pt p1, pt p2) {
+	line l;
+	if (fabs(p1.x - p2.x) < EPSILON) {
+		l.a = 1; l.b = 0.0; l.c = -p1.x;
+	} else {
+		l.a = -(double)(p1.y - p2.y) / (p1.x - p2.x);
+		l.b = 1.0;
+		l.c = -(double)(l.a * p1.x) - p1.y;
+	}
+	return l;
+}
+
+bool areParallel(line l1, line l2) {
+	return (fabs(l1.a - l2.a) < EPSILON) && (fabs(l1.b - l2.b) < EPSILON);
+}
+
+bool areSame(line l1, line l2) {
+	return areParallel(l1, l2) && (fabs(l1.c - l2.c) < EPSILON);
+}
+
+bool areIntersect(line l1, line l2, pt &p) {
+	if (areParallel(l1, l2)) return false;
+	p.x = (l2.b * l1.c - l1.b * l2.c) / (l2.a * l1.b - l1.a * l2.b);
+	if (fabs(l1.b) > EPSILON) p.y = -(l1.a * p.x + l1.c);
+	else p.y = -(l2.a * p.x + l2.c);
+	return true;
+}
+\ No newline at end of file