数学算法

				Function BS(N:integer; A:real):real;
				label 5,6,15;
				var
				    B:array[1..20] of real;
				    DEL,R,EPS,S,AK,A2,DA,AJP,AJM,Q1,Q2,OMEG:real;
				    M:integer;
				begin
				    If A = 0 Then
				    begin
				       If N / 2 = N / 2 Then
				       begin
				           B[N]:=0;
				           GoTo 15;
				       end;
				       B[N]:=2 / N;
				       GoTo 15;
				    end;
				    If Abs(A) < 8 Then
				    begin
				       DEL:=0.1e-7;
				       If N / 2  N / 2 Then
				       begin
				           R:=2 / N;
				           EPS:=R * DEL;
				           S:=R;
				           AK:=0;
				           A2:=A * A;
				5:         AK:=AK + 2;
				           R:=R * A2 * (N + AK - 2) / (AK * (AK - 1) * (N + AK));
				           S:=S + R;
				           If R > EPS Then GoTo 5;
				           B[N]:=S + R;
				           GoTo 15;
				       end;
				       R:=2 * A / (N + 1);
				       OMEG:=Abs(R * DEL);
				       S:=R;
				       AK:=1;
				       A2:=A * A;
				6:     AK:=AK + 2;
				       R:=R * A2 * (N + AK - 2) / (AK * (AK - 1) * (N + AK));
				       S:=S + R;
				       If Abs(R) > OMEG Then GoTo 6;
				       B[N]:=-(S + R);
				       GoTo 15;
				    end;
				    DA:=1 / A;
				    AJP:=DA * Exp(A);
				    AJM:=(DA * DA) / AJP;
				    B[1]:=AJP - AJM;
				    If N = 1 Then GoTo 15;
				    Q1:=-1;
				    Q2:=1;
				    For M:= 2 To N do
				    begin
				        B[M]:=Q1 * AJP - AJM + Q2 * DA * B[M - 1];
				        Q1:=-Q1;
				        Q2:=Q2 + 1;
				    end;
				15: BS:=B[N];
				end;