(*

PROCEDURE MakeAdjacentVertex(c,d: Corner; e: Corner) RAISES {ValidationError} =
  BEGIN
    IF IsIsolatedVertex(e) OR IsFaceWithNoBoundary(e) THEN 
      RAISE ValidationError("In InsertAdjacentVertex: the corner to be split MUST be an edge")
    ELSE
      c.oSplice(d);
      WITH
        be = e.borderOf(),
        es = e.cSym(),
        bes = es.borderOf()
      DO
        be.insertCorner(c);
        bes.insertCorner(d);
        IF IsRing(e) THEN 
          c.bLink(NIL,c);
          d.bLink(NIL,d);
          be.removeCorner(e);
          bes.removeCorner(es)
        ELSE
          c.bLink(e,e.bNext());
          d.bLink(es,es.bNext())
        END
      END
    END
  END MakeAdjacentVertex;

PROCEDURE Connect(c,d,nc,nd: Corner) : Face RAISES {ValidationError} = 
  BEGIN
    WITH
      bc = c.borderOf(),
      bd = d.borderOf(),
      f  = bc.faceOf()
    DO
      IF bd.faceOf() # f THEN 
        RAISE ValidationError("In connect, the two corners MUST be adjacent to a same face")
      ELSE
        IF AreSameCorner(c,d) THEN    (* creates a loop *)
          IF IsIsolatedVertex(d) THEN   
            nc.oSplice(nd);
            nc.bLink(NIL,nc);
            nd.bLink(NIL,nd);
            bd.removeCorner(d)    (* removing isolated vertex => removing border *)
          ELSE
            nc.oSplice(c);
            nd.oSplice(nc);
            nc.bLink(NIL,nc);
            nd.bLink(c.bPrev(),c);
            f.removeBorder(bc);
          END;
          WITH   
            fnc = CreateFace(),
            bnc = NEW(SMCorner.Border).init(nc),
            fnd = CreateFace(),
            bnd = NEW(SMCorner.Border).init(nd)
          DO 
            fnc.insertBorder(bnc);
            fnd.insertBorder(bnd)
          END
        ELSE      
          nc.oSplice(c);
          nd.oSplice(d);
          nc.bLink(c.bPrev(),d);
          nd.bLink(d.bPrev(),c);
          IF AreInSameBorder(c,d) THEN 
            f.removeBorder(bc);
            WITH
              fnc = CreateFace(),
              bnc = NEW(SMCorner.Border).init(nc),
              fnd = CreateFace(),
              bnd = NEW(SMCorner.Border).init(nd)
            DO
              fnc.insertBorder(bnc);
              fnd.insertBorder(bnd)
            END;
          ELSE
            f.removeBorder(bc);
            f.removeBorder(bd);
            WITH   
              fnc = CreateFace()
            DO
              fnc.insertBorder(bc);
              fnc.insertBorder(bd);
              WITH
                bc_bd  = fnc.joinBorders(bc,bd)
              DO
                bc_bd.insertCorner(nc);
                bc_bd.insertCorner(nd);
              END
            END
          END
        END;
        RETURN f
      END
    END  
  END Connect;




PROCEDURE Disconnect(c: Corner) 
*)