std::string operator[]

since C++20

// Non const version
constexpr reference operator[]( size_type pos );

// Const version
constexpr const_reference operator[]( size_type pos ) const;

until C++20

// Non const version
reference operator[]( size_type pos );

// Const version
const_reference operator[]( size_type pos ) const;

Returns a reference

to the element at specified index pos.

caution

No bounds checking is performed.

since C++11

If pos == size(), a reference to the character with value CharT() (the null character) is returned.

For the first (non-const) version, the behavior is undefined

if this character is modified to any value other than CharT().

until C++11

• (1) If pos == size(), the behavior is undefined.
• (2) If pos == size(), a reference to the character with value CharT() (the null character) is returned.

Parameters

• pos - position of the character to return

Return value

Reference to the requested character.

Exceptions

(none)

Complexity

Constant - O(1).

Example

Main.cpp

#include <iostream>
#include <string>
 
int main()
{
    std::string const e("Exemplar");
    for (unsigned i = e.length() - 1; i != 0; i /= 2)
        std::cout << e[i];
    std::cout << '\n';
 
    const char* c = &e[0];
    std::cout << c << '\n'; // print as a C string
 
    //Change the last character of s into a 'y'
    std::string s("Exemplar ");
    s[s.size()-1] = 'y'; // equivalent to s.back() = 'y';
    std::cout << s << '\n';
}

Output

rmx
Exemplar
Exemplary