The code demonstrates how to use function pointer to call a method via string using c++

cmdfy.cpp

/* Program Name : cmdfy
 * Developer : kawser
 * Developer Blog: http://blog.kawser.org
 * Blog Link: http://blog.kawser.org/2014/02/calling-cpp-function-fly.html
 *
 *
 * Objective : This code demonstrates how to use function pointer
 *                        to call a method via string 
 * 
 * IDEA : We will define some functions with similar signature and store these
 *        functions using function pointer into a map with string representation.
 *        Take input from user and parse the input and according to 
 *        input we will call the mapped method
 *        Otherwise show a error.          
 *                 
 *                
 * Prerequisites :map,vector,sstream
 * 
 * Exampe : 2
 */
 
 
 
#include <map>
#include <utility>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iostream>
 
 
 
using namespace std;
 
 
/* we will use the same signature for all functions */
/* signature : return type unsinged int and argument type unsigned int */
/* unsigned int limit: 0 to 65535 */ 
 
 
unsigned int square(unsigned int a){
 /* calculate square of a number and returns */
 return a*a;
}
 
 
unsigned int cube(unsigned int a){
 /* calculate cube of a number and returns */
 return a*a*a;
}
 
 
/*Renaming the signature*/
typedef unsigned int (*sig_ptr)(unsigned int);
 
 
void help(void){
 cout  << "Enter the following commands: without any space" <<endl;
 cout  <<"  1. square-number : to calcualte the square of the number"<<endl;
 cout <<"  2. cube-number : to calcuale the cube of the number"<< endl;
 cout <<"  3. -1 : to exit"<< endl<<endl; 
}
 
 
 
 
/*this the the parser of the command*/
 vector<string> &split(const string &s, char delim, vector<string> &elems) {
    stringstream ss(s);
    string item;
    while (getline(ss, item, delim)) {
        elems.push_back(item);
    }
    return elems;
}
vector<string> split(const string &s, char delim) {
    vector<string> elems;
    split(s, delim, elems);
    return elems;
}
 
 
 
 
int main(void){
 /* This is the Entry point of the program*/
 
 map < string , sig_ptr> mapped_functions;   // defining a map
 mapped_functions["square"] = square;          //  adding square into the map
 mapped_functions["cube"] = cube;                   //  adding cube into the map
 
 /*Enter into infinite loop*/
 for(;;){
  string cmd;        //command string
  help();                  //show the help
  cout<<endl;
  cout <<  "Enter a command : ";
  cin >> cmd ;
 
  if( cmd != "-1" ) {
   vector<string> cmds = split(cmd,'-');// parsing the command
   if (cmds.size() == 2){
    unsigned int  n  = atoi( cmds[1].c_str() );//converting the second 
                                               //argument into unsigned int
    if( mapped_functions.find(cmds[0]) != mapped_functions.end()  ) 
        cout <<cmd <<" : " <<mapped_functions[ cmds[0] ](n) <<endl;
   }
   else{
    cout<< "Invalid command"<<endl;
   }
   
  }
  else{
   break;
  }  
 
 
 }// End braces of for loop
 
 
 
 return 0;
}