一个简单的计算相对误差的小程序。基于winform，并设置了非空验证，当实际值或预测值或误差有一项为空时，通过按钮事件计算该数值-A simple calculation of the relative error of small procedures. Based on winform, and set a non-null authentication, when the actual value or the forecast error has a value or is empty,