1 files changed, 78 insertions, 0 deletions
diff --git a/lib/dihedral.h b/lib/dihedral.h
index c95b23a..f67c930 100644
--- a/lib/dihedral.h
+++ b/lib/dihedral.h
@@ -19,3 +19,81 @@ q_t *dihedral_gen_transformations(q_t q);
 R_t *dihedral_gen_involutions(q_t q);
 
 R_t factorial(q_t);
+
+#ifdef __cplusplus
+
+template <class T, q_t q>
+struct dihedral2_t { bool is_reflection; T x; };
+
+template <class T, q_t q>
+void init(dihedral2_t<T, q> *ptr) {
+  ptr->is_reflection = false;
+  ptr->x = (T)0;
+}
+
+template <class T, q_t q>
+dihedral2_t<T, q> copy(dihedral2_t<T, q> r) {
+  return r;
+}
+
+template <class T, q_t q>
+void free_spin(dihedral2_t<T, q> r) {
+  // do nothing!
+}
+
+template <q_t q>
+potts_t<q> act(dihedral2_t<q_t, q> r, potts_t<q> s) {
+  potts_t<q> s2;
+  if (r.is_reflection) {
+    s2.x = ((q + r.x) - s.x) % q;
+  } else {
+    s2.x = (r.x + s.x) % q;
+  }
+
+  return s2;
+}
+
+template <q_t q>
+dihedral2_t<q_t,q> act(dihedral2_t<q_t,q> r1, dihedral2_t<q_t,q> r2) {
+  dihedral2_t<q_t,q> r3;
+
+  if (r1.is_reflection) {
+    r3.is_reflection = !(r2.is_reflection);
+    r3.x = ((q + r1.x) - r2.x) % q;
+  } else {
+    r3.is_reflection = r2.is_reflection;
+    r3.x = (r1.x + r2.x) % q;
+  }
+
+  return r3;
+}
+
+template <q_t q>
+potts_t<q> act_inverse(dihedral2_t<q_t,q> r, potts_t<q> s) {
+  potts_t<q> s2;
+  if (r.is_reflection) {
+    s2.x = ((r.x + q) - s.x) % q;
+  } else {
+    s2.x = ((s.x + q) - r.x) % q;
+  }
+
+  return s2;
+}
+
+template <q_t q>
+dihedral2_t<q_t, q> act_inverse(dihedral2_t<q_t,q> r1, dihedral2_t<q_t,q> r2) {
+  dihedral2_t<q_t,q> r3;
+
+  if (r1.is_reflection) {
+    r3.is_reflection = !(r2.is_reflection);
+    r3.x = ((r1.x + q) - r2.x) % q;
+  } else {
+    r3.is_reflection = r2.is_reflection;
+    r3.x = ((r2.x + q) - r1.x) % q;
+  }
+
+  return r3;
+}
+
+#endif
+