基于模板字符串文字返回的c ++函数指针

Question

How can i return a function object based on a string literal argument?

This argument need not be a template, but I want to be able to input a string literal and return a function object

Im looking for something like:

template<const char * s> func_pointer(int arg);

I have tried returning a lambda. I have also tried returning a class operator() and a templated function. None work.

Any help is appreciated!

EDIT: calling the function with an extern variable will not work for my purposes either.

EDIT: I am writing a language parser. I want to build framework for the parser to avoid rewriting a lot of code. Therefore, I want to be able to have a bunch of functions that parse the text. I want to have a base function that parses a single string literal (the program is lexed.), and I want to be able to pass in the string for each possible base function.

EDIT: Note that any function object that can convert a lambda and a function pointer to a generalized type(like std::function) will do.

Answer 1

For me one of the easiest ways to map a string to a function is a map<string, function<int(int)> . Here's a simple example:

#include <string>
#include <iostream>
#include <functional>
#include <map>

int add(int a, int b){return a+b;}
int subtract(int a, int b){return a-b;}
int multiply(int a, int b){return a*b;}
int divide(int a, int b){return (b!=0?a/b: -1);}
map<string, function<int(int,int)>> functions = 
{
    {"add",add},
    {"subtract",subtract},
    {"multiply",multiply},
    {"divide",divide}
};

int main(int argc, char** argv)
{
    cout << functions["add"](5,2);
    return 0;
}

Answer 2

What I was looking for is the std::function object ( thanks to @tinstaafl ), this way I can have lambdas and function pointers convertible to te same type. A function can return a lambda based on a string literal.