求解用户定义的变量方程 [英] Solving a Variable Equation defined by the User

问题描述

非常感谢C，Python，C ++或Javascript的答案. 我读了几本书，做了所有的例子.现在，我想编写一个简单的程序. 但是，我已经遇到了以下障碍:

Answers in C, Python, C++ or Javascript would be very much appreciated. I've read a few books, done all the examples. Now I'd like to write a simple program. But, I already ran into the following roadblock:

我的目的是从用户那里获取一个方程式并将其保存在变量中， 例如:

My intention is to take an equation from the user and save it in a variable, For example:

-3*X+4 or pow(2,(sin(cos(x))/5))       >  [In valid C Math syntax]

然后为某个X值计算给定的表达式. 像这样:

And then calculate the given expression for a certain X-Value. Something like this:

printf("%g", UserFunction(3.2))   // Input 3.2 for X in User's Function and Print Result

有什么想法吗?对于我的一生，我无法弄清楚.更让我感到沮丧的是，该解决方案可能只是一个非常简单的解决方案.预先谢谢你.

Any ideas? For the life of me, I can't figure this out. Adding to my frustration, the solution is likely a very simply one. Thank you in advance.

推荐答案

在 C 中没有简单的方法可以做到这一点，但我认为 ExprTk 也是一个选项，但看起来是 C ++ 仅从正面看，获得有趣的结果要容易得多.

There isn't a simple way to do this in C but I think muParser may be useful to you, it is written in C++ but has C binding. ExprTk is also an option but looks like it is C++ only, on the plus side it looks much easier to get interesting results with.

另一个选择可以是表达式评估，它是 eval.h 标头对接口有一些很好的描述.

Another option may be the Expression Evaluation which is part of Libav. It is in C and the eval.h header has some good descriptions of the interface.

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