(* Algorithmus 6.1 *)
FUNCTION p(n:integer; VAR x,y:vektor; z: real):real;
VAR l,s : real; i,j: integer;
BEGIN
  s :=0;
  FOR i:=0 TO n DO
  BEGIN
    l:=1;
    FOR j:=0 TO n DO
    IF i<>j THEN l:=l*(z-x[j])/(x[i]-x[j]);
    s := s + l*y[i]
  END;
  p:=s
END;