我在NSString中有公式...如何评估它 [英] I have formula in a NSString... How to evaluate it

问题描述

可能重复：

什么是快速C或Objective-C数学解析器？

我有一个创建一个函数，它将公式作为NSString。我必须在String中替换一些东西并在执行公式后获取值。我怎么能这样做...

I have a create a function which takes a formula as a NSString. And I have to replace few things in the String and get the value after executing the formula. How can I do this...

Ex：NSString * formulaString = @（（A / B）-1）* 100;

Ex: NSString *formulaString = @"((A/B)-1)*100";

现在我可以将A替换为20，将B替换为10.
但是如何将计算值（（20/10）-1）* 100替换为100

Now I can replace A by 20, and B by 10. But how will get calculated value that is ((20/10)-1)*100 as 100

谢谢，
Ben

Thanks, Ben

推荐答案

你可以用以下字符替换这个方法

You can replace the characters by this method

NSString *formulaString = @"((A/B)-1)*100";

NSString *modifiedFormulaString = [formulaString stringByReplacingOccurrencesOfString:@"A" withString:@"10"];

modifiedFormulaString = [modifiedFormulaString stringByReplacingOccurrencesOfString:@"B" withString:@"10"];

但要计算数据，你需要使用一些解析器来解析它。

But to calculate dat u need to parse it using some parser.

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