> # Boehm Algorithmus
> restart: with(plots): with(linalg):
> boehm:=proc(degree,coeff,knot,x)
> # degree Grad der Splinekurve
> # coeff eine Koordinate der Kontrollpunkte
> # knot Knotenfolge (besitzt mindestens degree Werte mehr als coeff!)
> # einzufuegender Knoten x (muss groesser als knot[degree-1] sein!)
> # option trace;
> local i,j,n,m;
> global knotneu,coeff1;
> n:=vectdim(knot);
> #Berechnung der neuen Knotenfolge
> for i from degree-1 while x > knot[i] do i:=i+1 od;
> i:=i-1;
> knotneu:=vector(n+1);
> for j from 1 to i do knotneu[j]:=knot[j] od;
> knotneu[i+1]:=x;
> for j from n+1 by (-1) to i+2 do knotneu[j]:=knot[j-1] od;
> m:=vectdim(coeff);
> for j from 1 to i-degree+1 do coeff1[j]:=coeff[j] od;
> for j from i-degree+2  to i do
>   coeff1[j]:=((x-knot[j])*coeff[j]+(knot[j+degree-1]-x)*coeff[j-1])/(knot[j+degree-1]-knot[j]) od;
> for j from i+1 to m+1 do coeff1[j]:=coeff[j-1] od;
> end:
Warning, new definition for norm
Warning, new definition for trace
> knot:=vector(7, [1,2,3,4,5,6,7]):
> Curve:=array(1..4,1..2):
> coeffx:=vector(4,[5/2,7/2,9/2,11/2]):
> coeffy:=vector(4,[1,4,-1,2]):
> for j from 1 to 4 do Curve[j,1]:=coeffx[j]; Curve[j,2]:=coeffy[j] od:
> m:=3:
> x:=7/2:
> boehm(m,coeffx,knot,x):
> Curve1:=array(1..5,1..2):
> for j from 1 to 5 do Curve1[j,1]:=coeff1[j] od:
> boehm(m,coeffy,knot,x):
> for j from 1 to 5 do Curve1[j,2]:=coeff1[j] od:
> polygon1:=plot(convert(Curve,listlist)):
> polygon2:=plot(convert(Curve1,listlist)):
> display(polygon1,polygon2);
> 

>