unit2.pas

用于开发税务票据管理的软件

unit Unit2;

interface
uses
  Windows, Messages, SysUtils, Classes, Graphics,UNIT1, Controls, Forms, Dialogs;
Function BESSJ0(X:real):real;
Procedure ZBRAC(var X1, X2:real; SUCCES:boolean);

implementation
Function BESSJ0(X:real):real;
var
   AAA,BBB,CCC,Y,AX,Z,DDD,EEE,XX:real;
const
  P1=1;                    P2=-0.001098628627;
  P3=0.2734510407e-4;      P4=-0.2073370639e-5;
  P5=2.093887211E-07;
  Q1=-0.1562499995e-1;     Q2=0.1430488765e-3;
  Q3=-0.6911147651e-5;     Q4=7.621095161E-07;
  Q5=-9.34945152E-08;
  R1=57568490574;          R2=-13362590354;
  R3=651619640.7;          R4=-11214424.18;
  R5=77392.33017;          R6=-184.9052456;
  S1=57568490411;          S2=1029532985;
  S3=9494680.718;          S4=59272.64853;
  S5=267.8532712;          S6=1;
begin
  If Abs(X) < 8 Then
    begin
      Y:=X * X;
      BBB:=Y* (R4+ Y* (R5+ Y* R6));
      AAA:=R1+ Y* (R2+ Y* (R3+ BBB));
      CCC:=Y* (S3+ Y* (S4+ Y* (S5+ Y* S6)));
      BESSJ0:= AAA / (S1+ Y* (S2+ CCC));
    end
  Else
    begin
      AX:=Abs(X);
      Z:=8/ AX;
      Y:=Z* Z;
      XX:= AX- 0.785398164;
      CCC:=Y* (P3+ Y* (P4+ Y* P5));
      AAA:=P1+ Y* (P2+ CCC);
      DDD:=Y* (Q3+ Y* (Q4+ Y* Q5));
      EEE:=Z* Sin(XX) * (Q1+ Y* (Q2+ DDD));
      BESSJ0:= Sqrt(0.636619772 / AX) * (Cos(XX) * AAA- EEE);
    End;
End;

Procedure ZBRAC(var X1, X2:real; SUCCES:boolean);
var
    NTRY,J:integer;  FACTOR,F1,F2:real;
begin
    FACTOR:=1.6;
    NTRY:=50;
    If X1 = X2 Then ShowMessage('you have to guess an initial range');
    F1:=FUN(X1);
    F2:=FUN(X2);
    SUCCES:=True;
    For J:=1 To NTRY do
    begin
        If F1 * F2 < 0 Then Exit;
        If Abs(F1) < Abs(F2) Then
        begin
            X1:=X1 + FACTOR * (X1 - X2);
            F1:=FUN(X1);
        end
        Else
        begin
            X2:=X2 + FACTOR * (X2 - X1);
            F2:=FUN(X2);
        end;
    end; 
    SUCCES:=False;
end;

end.