qtrap.dem

来自「Delphi Pascal 数据挖掘领域算法包 数值算法大全」· DEM 代码 · 共 36 行

PROGRAM d4r2(input,output);
(* driver for routine QTRAP *)
CONST
   pio2=1.5707963;
VAR
   glit : 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 *)

(*$I QTRAP.PAS *)

BEGIN
   a := 0.0;
   b := pio2;
   writeln ('Integral of func computed with QTRAP');
   writeln;
   writeln ('Actual value of integral is',fint(b)-fint(a):12:6);
   qtrap(a,b,s);
   writeln ('Result from routine QTRAP is',s:12:6);
END.