C++ 将字符串转换为数学计算

Convert string to mathematical evaluation

提问by Anton

Okay, so what I want to do is to use a string as input (for instance "16*12+25"), convert it to a mathematical evaluation that the computer can comprehend and return the evaluated value. I could probably write this myself, but it would most likely take quite a while and in the end, it still wouldn't end up as good as I'd like it to unless I want to put even more time into it.

好的，那么我想要做的是使用一个字符串作为输入（例如“16 * 12 + 25”），将其转换为计算机可以理解的数学评估并返回评估值。我可能会自己写这个，但它很可能需要很长时间，最后，除非我想投入更多时间，否则它仍然不会像我希望的那样好。

So my question is, is there any script, library or api that you know can do this for C++? I have found some for both java, python and .NET. But I am not working with any of these languages and I would like to remain within C++ for as long (hopefully throughout the entire project) as possible. Do you have any good ideas or links?

所以我的问题是，你知道有没有任何脚本、库或 API 可以为 C++ 做到这一点？我找到了一些适用于 java、python 和 .NET 的方法。但我不使用任何这些语言，我希望尽可能长时间地（希望在整个项目中）留在 C++ 中。你有什么好的想法或链接吗？

回答by Anton

I found what I was looking for! The downloadable source is C++ and a CodeBlocks project. You can find it here: http://www.speqmath.com/tutorials/expression_parser_cpp/index.html

我找到了我要找的东西！可下载的源是 C++ 和一个 CodeBlocks 项目。你可以在这里找到它：http: //www.speqmath.com/tutorials/expression_parser_cpp/index.html

A far more sophisticated expression parser recommended by Jared: http://www.partow.net/programming/exprtk/index.html

Jared 推荐的更复杂的表达式解析器：http: //www.partow.net/programming/exprtk/index.html

回答by spencercw

There is nothing built into C++ for this; all the expression parsing code belongs in the compiler. You will need to use some external library. A quick Google search brings up muParserwhich looks pretty reasonable.

C++ 没有为此内置任何东西；所有的表达式解析代码都属于编译器。您将需要使用一些外部库。一个快速的谷歌搜索带来了看起来很合理的muParser。