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std::basic_string_view<CharT,Traits>:: operator[]

From cppreference.net
C++
Strings library
std::basic_string_view
constexpr const_reference operator [ ] ( size_type pos ) const ;
(since C++17)

Returns a const reference to the character at specified location pos .

If pos < size ( ) is false , the behavior is undefined.

(until C++26)

If pos < size ( ) is false :

  • If the implementation is hardened , a contract violation occurs. Moreover, if the contract-violation handler returns under “observe” evaluation semantic, the behavior is undefined.
  • If the implementation is not hardened, the behavior is undefined.
(since C++26)

Contents

Parameters

pos - position of the character to return

Return value

data_  [ pos ]

Exceptions

Does not throw.

Complexity

Constant.

Notes

Unlike std::basic_string::operator[] , std :: basic_string_view :: operator [ ] ( size ( ) ) does not return a reference to CharT ( ) .

Example

Run this code 
#include <iostream>
#include <string_view>
int main()
{
    std::string str = "Exemplar";
    std::string_view v = str;
    std::cout << v[2] << '\n';
//  v[2] = 'y'; // Error: cannot modify through a string view
    str[2] = 'y';
    std::cout << v[2] << '\n';
}

Output: 

e
y

See also

accesses the specified character with bounds checking
(public member function)
accesses the specified character
(public member function of std::basic_string<CharT,Traits,Allocator> )