Convert std::string to existing function with parameters in C++
c++, function
Solution
You cannot in general execute code in C++ whose source is contained in a string. Probably the most compelling motivation for this is so that a C++ implementation is not required to have a C++ compiler on the machine that the code runs on, although there is more to it than just that.
You may be able to do it for specific cases. That could be:
Platform-specific, for example:
- Wrap the source up in some boilerplate, then either call the compiler externally, link against it, or embed it in your program. This gives you a program or library.
- Run that new program externally, or dynamically link against that library.
Input-specific, for example:
- You could parse a function call to a particular known function, with literals as arguments, relatively easily without needing a complete C++ compiler. Get the argument values out into variables and call the function. But if you're going to do that, you could specify a more easily parsable format for the string, than one that looks like a C++ function call.
It sounds as though in your task you have a string that is one of:
- a representation of an `int`
- a representation of a `double`
- a representation of a date and time.
You don't say what you want to do with this string, but whatever that is you probably need to (a) examine the string to find out which of the three it is, and then (b) do something appropriate to that format. Better, you could give the derived class the responsibility of returning the same representation no matter which of the three `GetValue()` returns. For example, if what you really want is seconds since 1970, add a `GetSecondsSinceEpoc` function, and implement it differently in each class.
Problem
I've got an implemented function `MyFunc(int, double, string)` in my project. How can I call this function with necessary parameters having its string representation, for example ``` std::string str = "MyFunc(2, 3.12, \"Lemon Juice\")"; ``` And what about the standard functions, for example, how can I call `time()` having `std::string "time()"`? Ok, here's more detailed task. I've got a `map <string, Data>` `Data` is a class-wrapper with many childs. When I call `Data.GetValue()` method, it returns a `std::string`, depending of child class inner data. One of `Data` childs must return the string representation of `int`, another - the string representation of `double`, and the last one - the string representation of current date and time. Here's the problem - I don't know how to call the standard function `ctime()` for getting information from one of `Data` childs.