Question

I am new to C++ and am not able to correctly define maps in class definition.

Here is the code I have written:

#include<stdio.h>
#include <iostream>
#include <map>
#include <utility> // make_pair
#include <string.h>
#include <sstream>

using namespace std;

class assgnt
{
private:
    //typedef std::map<int, int> MapType;
    //MapType my_map;
public:
    bool isGoodPoint(int x, int y);
    void addGoodNeighbours(int x, int y);

};

inline bool assgnt::isGoodPoint(int x, int y)
{
    string xs, ys;
    stringstream xout, yout;
    int xsum=0, ysum=0;

    xout<<x; yout<<y;

    xs = xout.str();
    ys = yout.str();

    for each (char c in xs)
    {
        xsum = xsum + int(c);
    }

    for each (char c in ys)
    {
        ysum = ysum + int(c);
    }

    if (xsum+ysum <= 19)
        return true;
    else 
        return false;
}

inline void assgnt::addGoodNeighbours(int x, int y)
{
    //if assgnt::isGoodPoint(x+1,y)
    if(isGoodPoint(x+1,y))
    {

    }
    /*if isGoodPoint(x+1,y) and [x+1,y] not in points: points.append([x+1,y])
    if isGoodPoint(x-1,y) and [x-1,y] not in points: points.append([x-1,y])
    if isGoodPoint(x,y+1) and [x,y+1] not in points: points.append([x,y+1])
    if isGoodPoint(x,y-1) and [x,y-1] not in points: points.append([x,y-1])*/
}


int main()
{

   typedef std::map<int, int> MapType;
    MapType my_map;

    // insert elements using insert function
    my_map.insert(std::pair<int, int>(0, 0));

    int i=0;

    while true
    {


    //my_map.insert(std::pair<int, int>(2, 2));
    //my_map.insert(std::pair<int, int>(3, 3));
    //my_map.insert(MapType::value_type(4, 4)); // all standard containers provide this typedef
    //my_map.insert(std::make_pair(5, 5));      // can also use the utility function make_pair

    MapType::iterator iter = my_map.begin();

    std::cout << "Size of my_map: " << my_map.size() << '\n';

    std::cout << "Enter a key to search for: ";
    int c;
    std::cin >> c;

    iter = my_map.find(c);
    if (iter != my_map.end()) 
    {
        int num = iter->second;
        if(num == 0)
            std::cout << "Value is found: " << iter->second << '\n';
        else 
            std::cout << "Value not found: ";
    }
    else
        std::cout << "Key is not in my_map" << '\n';

//    my_map.clear();
}

I wish to define the map typedef std::map MapType; in the class definition, so that I can use it in all inline functions and the main() by creating its object.

Please help.

Answer 1

I suppose you want to use it outside of the class? Define it in a public section and be happy. Typedefs are absolutely safe from encapsulation point of view, they are just synonyms. Then you can use it in main as assgnt::MapType.