cal

代码说明：

  计算式的计算，能用字符的形式完成大部分的计算，应该有不少人编了此程序，但是这个还是有新颖之处，完全是对字符处理产生的计算，可以使用全角计算符，对三角函数，科学计数等有很好的支持，算是我对字符串处理一个探索成果。(Formula calculation, can be used to complete most of the characters in the form of calculation, should be compiled of the many people in this process, but this is still a novelty, is Zifu handling to complete the calculation, you can use full-width calculation breaks, on trigonometric functions, scientific counting good support, I suppose I deal with an exploration of the string results.)