Character Array as a value in C++ map

Question

I want to define something like

Map myMap;

The above declaration is accepted by c++ compiler and no error is thrown bu

Answer 1

According to documentation pair can hold (and be defined for) distinct classes. C array is not a class, but a construct. You must define your own class with overloaded operator[](). Might need comparison operators as well

Answer 2

You cannot use an array in a standard container.

1. Use an std::vector instead of an array

2. Use a map of pointers to arrays of 5 elements.

3. Use boost tuples instead of arrays of 5 elements.

4. Instead of using an array make a new struct that takes 3 elements. Make the map<int, newstructtype>. Or wrap your array in a struct and that will work too.

\

struct ArrayMap
{
    int color[5];
};

/

Answer 3

One way is to wrap the fixed size character array as a struct.

struct FiveChar
{
   FiveChar(char in[5]) { memcpy(data, in, 5); }
   char& operator[](unsigned int idx) { return data[idx]; }
   char data[5];
};

int main(void)
{
   char arr[5] = "sdf";
   map<int, FiveChar> myMap;
   myMap.insert(pair<int, FiveChar>(0, arr));
   return 0;
}

Answer 4

I understand your performance requirements (since I do similar things too), but using character arrays in that way is rather unsafe.

If you have access to C++11 you could use std::array. Then you could define your map like:

map <int, array<char, 5>> myMap;

If you cannot use C++11, then you could use boost::array.