unit2.pas

1、说明： 本书中所有的常用数值算法子过程按书中的章数分别放在以C开头的子目录中。 所有这些为验证上述子过程而编的验证过程按书中的章数分别放在以D开头的子目录中。 所有为验

unit Unit2;

interface
Function BESSY0(X:real):real;
Function BESSJ0(X:real):real;

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;

Function BESSY0(X:real):real;
var
  AAA,BBB,Z,Y,XX,CCC:real;
const
    P1 = 1;                  P2 = -0.001098628627;
    P3 = 0.2734510407e-4;    P4 = -0.2073370639e-5;
    P5 = 2.093887211E-07;
    Q1 = -0.01562499995;     Q2 = 0.1430488765e-3;
    Q3 = -0.6911147651e-5;   Q4 = 7.621095161E-07;
    Q5 = -9.34945152E-08;
    R1 = -2.957821389E9;     R2 = 7.062834065E9;
    R3 = -512359803.6;       R4 = 10879881.29;
    R5 = -86327.92757;       R6 = 228.4622733;
    S1 = 40076544269;        S2 = 745249964.8;
    S3 = 7189466.438;        S4 = 47447.2647;
    S5 = 226.1030244;        S6 = 1;
begin
    If X < 8 Then
    begin
        Y:=X * X;
        AAA:=R1 + y * (R2 + y * (R3 + y * (R4 + y * (R5 + y * R6))));
        BBB:=S1 + y * (S2 + y * (S3 + y * (S4 + y * (S5 + y * S6))));
        BESSY0:=AAA / BBB + 0.636619772 * BESSJ0(X) * Ln(X);
    end
    Else
    begin
        Z:=8 / X;
        y:=Z * Z;
        XX:=X - 0.785398164;
        AAA:=Sqrt(0.636619772 / X);
        BBB:=P1 + y * (P2 + y * (P3 + y * (P4 + y * P5)));
        CCC:=Q1 + y * (Q2 + y * (Q3 + y * (Q4 + y * Q5)));
        BESSY0:=AAA * (Sin(XX) * BBB + Z * Cos(XX) * CCC);
    end;
end;

end.