chapter x. example 3. construction and evaluation of the pp-representat-
c                     ion of a b-spline.
c  from  * a practical guide to splines *  by c. de boor
calls bsplpp(bsplvb),ppvalu(interv)
c
      integer ia,l
      real bcoef(7),break(5),coef(4,4),scrtch(4,4),t(11),value,x
c                set knot sequence  t  and b-coeffs for  b(4,4,t)  ....
      data t / 4*0.,1.,3.,4.,4*6. /, bcoef / 3*0.,1.,3*0. /
c                          construct pp-representation  ....
      call bsplpp ( t, bcoef, 7, 4, scrtch, break, coef, l )
c
c     as a check, evaluate  b(4,4,t)  from its pp-repr. on a fine mesh.
c             the values should agree with (some of) those generated in
c                        example 2 .
      do 20 ia=1,40
         x = float(ia)/5. - 1.
         value = ppvalu ( break, coef, l, 4, x, 0 )
   20    print 620, x, value
  620 format(f10.1,f20.8)
                                        stop
      end