std::basic_string<CharT,Traits,Allocator>::at (3) - Linux Manuals

std::basic_string<CharT,Traits,Allocator>::at: std::basic_string<CharT,Traits,Allocator>::at

NAME

std::basic_string<CharT,Traits,Allocator>::at - std::basic_string<CharT,Traits,Allocator>::at

Synopsis

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