用于开发税务票据管理的软件

				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;