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How do I create a function pointer that someone could use for their own implementation from another class and store it?

Paul Arnold 1 Reputation point
2022-12-06T01:33:10.017+00:00

What I want is to make an interpreter. I want to implement a way for people to define their own functions. I think this would also be used for functions that should be included like 'sin()' anyway this is the code in the form of the relevant parts: 

//LineEval.h  
  
#include <vector>  
#include <functional>  
#include <string>  
  
class LineEval  
{  
public:  
	void setFunction(std::string name, std::function<outard(inargs)> &address);  
private:  
	std::vector<std::function<outard(inargs)>> ops;  
	std::vector<std::string> funNames;  
}  
  
//LineEval.cpp  
void LineEval::setFunction(std::string name, std::function<outard(inargs)> &address)  
{  
	funNames.push_back(name);  
	ops.push_back(address);  
	  
	  
}  
  
//Source.cpp  
#include "LineEval.h"  
  
outard sin(inargs) {  
  
}  
  
int main()  
{  
    LineEval eval;  
    eval.setFunction("sin", sin);  
}//LineEval.h  
  
#include <vector>  
#include <functional>  
#include <string>  
  
class LineEval  
{  
public:  
	void setFunction(std::string name, std::function<outard(inargs)> &address);  
private:  
	std::vector<std::function<outard(inargs)>> ops;  
	std::vector<std::string> funNames;  
}  
  
//LineEval.cpp  
void LineEval::setFunction(std::string name, std::function<outard(inargs)> &address)  
{  
	funNames.push_back(name);  
	ops.push_back(address);  
	  
	  
}  
  
//Source.cpp  
#include "LineEval.h"  
  
outard sin(inargs) {  
  
}  
  
int main()  
{  
    LineEval eval;  
    eval.setFunction("sin", sin);  
}

I also might want to call 'setFunction()' from another class.

Developer technologies | C++

1 answer

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  1. Minxin Yu 13,506 Reputation points Microsoft External Staff
    2022-12-06T06:08:29.003+00:00

    Hi, @Paul Arnold

    You can refer to the snippet below: 

     //LineEval.h  
      
 #include <vector>  
 #include <functional>  
 #include <string>  
  
class LineEval  
{  
public:  
    void setFunction(std::string name, std::function<void(int)> address);  
    void playFunction(int pos,int para);  
    void playFunction(std::string FunName,int para);  
  
private:  
    std::vector<std::function<void(int)>> ops;  
    std::vector<std::string> funNames;  
};  
  
  
  
//LineEval.cpp  
#include"LineEval.h"  
void LineEval::setFunction(std::string name, std::function<void(int)> address)  
{  
    funNames.push_back(name);  
    ops.push_back(address);  
  
}  
    void LineEval::playFunction(int pos,int para)  
  {  
        ops[pos](para);  
    }  
    void LineEval::playFunction(std::string FunName,int para)  
    {  
          
        auto it = std::find(funNames.begin(), funNames.end(), FunName);  
        if(it!= funNames.end())  
            ops[std::distance(funNames.begin(), it)](para);  
           
        else {}  
    }  

//Source.cpp  
#include<iostream>  
 #include "LineEval.h"  
void  sinX (int para) {  
    std::cout << "hello"<< para<<std::endl;  
}  
  
  
int main()  
{  
    LineEval eval;  
    eval.setFunction("sinX", sinX);  
    eval.playFunction("sinX",23);  
    eval.playFunction(0, 123);  
  
}

    Best regards,

    Minxin Yu

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