std::basic_string::at

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::operator= basic_string::assign basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (C++11) basic_string::back (C++11) basic_string::data basic_string::c_str Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (C++11)

Operations basic_string::clear basic_string::insert basic_string::erase basic_string::push_back basic_string::pop_back (C++11) basic_string::append basic_string::operator+= basic_string::compare basic_string::replace basic_string::substr basic_string::copy basic_string::resize basic_string::swap Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of Constants basic_string::npos

Non-member functions operator+ operator==operator!=operator<operator>operator<=operator>= swap(std::basic_string) operator<<operator>> getline stoistolstoll (C++11)(C++11)(C++11) stoulstoull (C++11)(C++11) stofstodstold (C++11)(C++11)(C++11) to_string (C++11) to_wstring (C++11) Helper classes hash<std::string>hash<std::wstring>hash<std::u32string>hash<std::u16string> (C++11)(C++11)(C++11)(C++11)

 

reference       at( size_type pos );
const_reference at( size_type pos ) const;

Returns a reference to the character at specified location pos. Bounds checking is performed, exception of type std::out_of_range will be thrown on invalid access.

Parameters

pos

-

position of the character to return

Return value

Reference to the requested character.

Exceptions

Throws std::out_of_range if pos >= size().

Complexity

Constant.

Example

Run this code

#include <stdexcept>
#include <iostream>
#include <string>
 
int main()
{
    std::string s("message"); // for capacity
 
    s = "abc";
    s.at(2) = 'x'; // ok
    std::cout << s << '\n';
 
    std::cout << "string size = " << s.size() << '\n';
    std::cout << "string capacity = " << s.capacity() << '\n';
 
    try {
        // throw, even if capacity allowed to access element
        s.at(3) = 'x';
    }
    catch (std::out_of_range const& exc) {
        std::cout << exc.what() << '\n';
    }
}

Output:

abx
string size = 3
string capacity = 7
basic_string::at

See also

operator[]

access specified character (public member function)