how to write operator overloading for operator [] in c++

Question

I want to make three[0]='p'; work in the code below. I think I have to make an operator overloading for that but I don't know how to do. What I want to get is to change first index of "Lottery winner!" to 'p'. (To get "pottery winner!").

#include<iostream>
#include<cstring>
using namespace std;

class str
{
    char* a;
 public:
    str(char *aa=""){
    this->a = new char[strlen(aa)+1];
    strcpy(a,aa);
}

~str(){
    delete a;
}

friend ostream& operator<<(ostream &out, str &aa);
friend istream& operator>>(istream &in, str &aa);

};
ostream& operator<<(ostream &out, str &aa){ 
    out<<aa.a;
    return out;
}

istream& operator>>(istream &in, str &aa){
    in>>aa.a;
    return in;
}

void main(){
  str three("Lottery winner!");
  three[0]='p';
  cout<<three<<endl;
}

Possible duplicate of [What are the basic rules and idioms for operator overloading?](https://stackoverflow.com/questions/4421706/what-are-the-basic-rules-and-idioms-for-operator-overloading) — user0042, Oct 11 '17 at 07:10

OutOfBound · Answer 1 · 2017-10-11T22:44:30.423

1

This is the general signature of the operator[]:

T& operator[](any_type);

In your context it would look like this:

struct str {

    ...

    char& operator[](std::size_t pos) {
        return a[pos];
    }

};

edited Oct 11 '17 at 22:44

answered Oct 11 '17 at 07:15

OutOfBound

1,914
14
31

score 0 · Answer 2 · answered Oct 11 '17 at 07:18

0

class str
{
    // ...
public:
    // ...
    char& operator[] (int x) 
    {
      // add array out-of-bounds check here if you like to ...
      return a[x];
    }
}

answered Oct 11 '17 at 07:18

Marco Freudenberger

636
6
13

1

Bounds checking is usually only done with the `at()` method. – OutOfBound Oct 11 '17 at 09:08

score 0 · Answer 3 · answered Oct 11 '17 at 07:25

0

operator char*() 
{
    return a; 
}

Could also work

answered Oct 11 '17 at 07:25

unknown

368
4
12

how to write operator overloading for operator [] in c++

3 Answers3