求最大公因數的三種表示法

一	Function GCD(ByVal a%, ByVal b%)         Do Until a = b             If a > b Then a -= b             If a < b Then b -= a         Loop         GCD = a     End Function
二	Function GCD(ByVal a%, ByVal b%)         GCD = If(b = 0, a, GCD(b, a Mod b))     End Function
三	Function GCD(ByVal a%, ByVal b%)         If b = 0 Then             GCD = a         Else             GCD = GCD(b, a Mod b)         End If     End Function