trapzd.dem

Delphi Pascal 数据挖掘领域算法包 数值算法大全

PROGRAM d4r1(input,output);
(* driver for routine trapzd *)
CONST
   nmax=14;
   pio2=1.5707963;
VAR
   glit : integer;
   i : integer;
   a,b,s : real;

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

FUNCTION fint(x : real) : real;
(* Integral of test function *)
BEGIN
   fint := 4.0*x*(sqr(x)-7.0)*sin(x)-
         (sqr(sqr(x))-14.0*sqr(x)+28.0)*cos(x);
END;

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

BEGIN
   a := 0.0;
   b := pio2;
   writeln ('integral of func with 2^(n-1) points');
   writeln ('actual value of integral is',fint(b)-fint(a):12:6);
   writeln ('n':6,'approx. integral':24);
   FOR i := 1 to nmax DO BEGIN
      trapzd(a,b,s,i);
      writeln (i:6,s:20:6)
   END
 END.