NRBSQUARE: create the NURBS surface for a square.

 Calling Sequence:
 
 srf = nrbsquare (corner, lengthx, lengthy);
 srf = nrbsquare (corner, lengthx, lengthy, degree);
 srf = nrbsquare (corner, lengthx, lengthy, degree, nsub);

 INPUT:
   corner  : the coordinates of the bottom left corner of the square. 
   lenghtx : the length along the x direction.
   lenghty : the length along the y direction.
   degree  : the degree of the NURBS surface, in each direction.
   nsub    : the number of subdivision of the NURBS surface, in each direction.

 OUTPUT:
   srf     : the NURBS surface.

    Copyright (C) 2016 Jacopo Corno, Rafael Vazquez

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

Package: nurbs