PROGRAM d5r8(input,output);
(* driver for routine CHEBPC *)
LABEL 10,99;
CONST
   nval=40;
   pio2=1.5707963;
TYPE
   glcarray= ARRAY [1..nval] OF real;
VAR
   a,b,poly,x,y : real;
   i,j,mval : integer;
   c,d : glcarray;

FUNCTION func(x: real): real;
BEGIN
   func := sqr(x)*(sqr(x)-2.0)*sin(x)
END;

(*$I MODFILE.PAS *)
(*$I CHEBFT.PAS *)

(*$I CHEBPC.PAS *)

BEGIN
   a := -pio2;
   b := pio2;
   chebft(a,b,c,nval);
10:   writeln;
   writeln('How many terms in Chebyshev evaluation?');
   write('Enter n between 6 and ',nval:2,
         '. (n := 0 to end).  ');
   readln(mval);
   IF ((mval <= 0) OR (mval > nval)) THEN GOTO 99;
   chebpc(c,d,mval);
(* test polynomial *)
   writeln;
   writeln('x':9,'actual':14,'polynomial':14);
   FOR i := -8 to 8 DO BEGIN
      x := i*pio2/10.0;
      y := (x-(0.5*(b+a)))/(0.5*(b-a));
      poly := d[mval];
      FOR j := mval-1 DOWNTO 1 DO BEGIN
         poly := poly*y+d[j]
      END;
      writeln(x:12:6,func(x):12:6,poly:12:6)
   END;
   GOTO 10;
99:
END.