设计一个简单的计算器，能够进行加法、减法、乘法和除法功能(整数和浮点数)。格式是先输入一个数，然后输入运算符号，输入另一个数字，最后输出结果。-Design a simple calculator capable of addition, subtraction, multiplication and division functions (integer and floating-point numbers). The format is to enter a number, then enter operational sign, enter another number, last output.