git release.HEADmaster

1 files changed, 40 insertions, 0 deletions

diff --git a/util.c b/util.c
new file mode 100644
index 0000000..ef31bde
--- /dev/null
+++ b/util.c
@@ -0,0 +1,40 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+#include "dat.h"
+#include "fns.h"
+
+double
+round(double n)
+{
+	return floor(n + 0.5);
+}
+
+Point
+rotatept(Point p, double θ, Point c)
+{
+	Point r;
+
+	p = subpt(p, c);
+	r.x = round(p.x*cos(θ) - p.y*sin(θ));
+	r.y = round(p.x*sin(θ) + p.y*cos(θ));
+	r = addpt(r, c);
+	return r;
+}
+
+int
+ptincircle(Point p, Point c, double r)
+{
+	Point d;
+
+	d = subpt(c, p);
+	return hypot(d.x, d.y) < r;
+}
+
+int
+triangleXcircle(Triangle t, Point c, double r)
+{
+	return ptincircle(t.p0, c, r) ||
+		ptincircle(t.p1, c, r) ||
+		ptincircle(t.p2, c, r);
+}