bessy0.txt

用于开发税务票据管理的软件

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;