refactored binarytiling::parabolic to parabolic1 in hyperpoint

hyperpoint.cpp

@@ -319,6 +319,10 @@ transmatrix ypush(ld alpha) {
   return T;
   }
 
+transmatrix parabolic1(ld u) {
+  return transmatrix {{{-u*u/2+1, u, u*u/2}, {-u, 1, u}, {-u*u/2, u, u*u/2+1}}};
+  }
+
 // rotate the hyperbolic plane around C0 such that H[1] == 0 and H[0] >= 0
 transmatrix spintox(const hyperpoint& H) {
   transmatrix T = Id;