1 files changed, 46 insertions, 0 deletions
diff --git a/lib/circle_group.h b/lib/circle_group.h
new file mode 100644
index 0000000..cb7cadd
--- /dev/null
+++ b/lib/circle_group.h
@@ -0,0 +1,46 @@
+#pragma once
+
+#include "angle.h"
+
+class circle_group_t {
+  public:
+    bool is_reflection;
+    double x;
+
+    circle_group_t() : is_reflection(false), x(0) {}
+    circle_group_t(bool x, double y) : is_reflection(x), x(y) {}
+
+    angle_t act(const angle_t& theta) const {
+      if (is_reflection) {
+        return angle_t(fmod(2 * M_PI + x - theta.x, 2 * M_PI));
+      } else {
+        return angle_t(fmod(x + theta.x, 2 * M_PI));
+      }
+    }
+
+    circle_group_t act(const circle_group_t& r) const {
+      if (is_reflection) {
+        return circle_group_t(!r.is_reflection, fmod(2 * M_PI + x - r.x, 2 * M_PI));
+      } else {
+        return circle_group_t(r.is_reflection, fmod(x + r.x, 2 * M_PI));
+      }
+    }
+
+    angle_t act_inverse(const angle_t& theta) const {
+      if (is_reflection) {
+        return act(theta);
+      } else {
+        return angle_t(fmod(2 * M_PI + theta.x - x, 2 * M_PI));
+      }
+    }
+
+    circle_group_t act_inverse(const circle_group_t& r) const {
+      if (is_reflection) {
+        return act(r);
+      } else {
+        return circle_group_t(r.is_reflection, fmod(2 * M_PI + r.x - x, 2 * M_PI));
+      }
+    }
+};
+
+