Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

string::at

Return a character with bounds checking.

char&
at(
    std::size_t pos);
  » more...

char const&
at(
    std::size_t pos) const;
  » more...