gcf.txt

特殊函数 1.г函数、贝塔函数、阶乘及二项式系数 2.不完全г函数、误差函数 3.不完全贝塔函数

procedure GCF(var GAMMCF:real; A:real; X:real; var GLN:real);
label 1;
const
  ITMAX=100;    EPS=0.0000003;
var
  N:integer; GOLD,G,FAC,B1,B0,ANF,ANA,AN,A1,A0:real;
begin
  GLN:=GAMMLN(A);
  GOLD:=0;
  A0:=1;
  A1:=X;
  B0:=0;
  B1:=1;
  FAC:=1;
  For N:=1 To ITMAX do
  begin
    AN:=N;
    ANA:=AN - A;
    A0:=(A1 + A0 * ANA)* FAC;
    B0:=(B1 + B0 * ANA)* FAC;
    ANF:=AN * FAC;
    A1:=X * A0 + ANF * A1;
    B1:=X * B0 + ANF * B1;
    If A1 <> 0 Then
    begin
      FAC:=1 / A1;
      G:=B1 * FAC;
      If Abs((G - GOLD)/ G)< EPS Then GoTo 1;
      GOLD:=G;
    end
  end;
  ShowMessage('A too large, ITMAX too small');
1: GAMMCF:=Exp(-X + A * Ln(X)- GLN)* G;
end;