用于开发税务票据管理的软件

				procedure GSER(var GAMSER:real; A:real; X:real; var GLN:real);
				label 1;
				const
				  ITMAX=100;    EPS=0.3E-6;
				var
				  N:Integer;
				  SUM,DEL,AP:Real;
				begin
				  GLN:=GAMMLN(A);
				  If X 				    If X < 0 Then
				    begin
				        ShowMessage('警告：X				        goto 1;
				    end
				  else
				  begin
				      GAMSER:=0;
				      goto 1;
				  end;
				  AP:=A;
				  SUM:=1 / A;
				  DEL:=SUM;
				  For N:=1 To ITMAX do
				  begin
				      AP:=AP + 1;
				      DEL:=DEL * X / AP;
				      SUM:=SUM + DEL;
				      If Abs(DEL) < Abs(SUM) * EPS Then GoTo 1;
				  end;
				  ShowMessage('A too large, ITMAX too small');
				1: GAMSER:=SUM * Exp(-X + A * Ln(X) - GLN);
				end;