CODEWITHSUNDEEP
c++arraysdictionarystl
Agrudge Amicus
Agrudge Amicus

Reputation: 1103

using character array as a key in map

I am trying to use char[] as a key for a map:

#include<iostream>
#include<map>
#include<string>
#include<utility>
#include<list>

using namespace std;

int main(void)
{
    map<char[10],int> m;

    char c[10]={'1','2','3','4','5','6','7','8','9','0'};
    m[c]=78;
    return 0;
}

But is throwing an error:

error: array used as initializer

second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)

even this doesn't work: m["abcdefghi"]=4;

How to use char [] as a key? I have couple of questions on SO but they didn't help much.

NOTE: I have used string but I want to try char[] just for curiosity

Upvotes: 2

Views: 1187

Answers (2)

Aykhan Hagverdili
Aykhan Hagverdili

Reputation: 29985

Use std::array:

#include <array>
#include <iostream>
#include <map>

int
main()
{
  using key_type = std::array<char, 10>;
  std::map<key_type, int> m;

  key_type c{ '1', '2', '3', '4', '5', '6', '7', '8', '9', '0' };
  m[c] = 78;
}

If you want variable size, use std::string_view:

#include <iostream>
#include <map>
#include <string_view>

int
main()
{
  std::map<std::string_view, int> m;

  char c[10] = { '1', '2', '3', '4', '5', '6', '7', '8', '9', '0' };
  m[{c, sizeof(c)}] = 78;
}

Upvotes: 0

Vlad from Moscow
Vlad from Moscow

Reputation: 310990

Arrays have neither the copy constructor nor the copy assignment operator. And there is no default operator < for arrays.

Instead of array use the standard container std::array.

For example

#include<iostream>
#include <array>
#include<map>

int main()
{
    std::map< std::array<char, 10>, int> m;

    std::array<char, 10> c = {'1','2','3','4','5','6','7','8','9','0'};
    m[c]=78;

    return 0;
}

Upvotes: 3

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