Third the series of influential, important, and indispensible guides to modern C++ practice. C++ is a difficult language to use well, and common practice has changed radically over the years. A big part of using C++ effectively is mastering idioms -- code snippets that everyone should understand but whose meaning isn't obvious at first inspection. The Standard Template Library (STL) is just three years old, and it's chock-full of idioms and traps for the unwary. Used well, though, it's a powerful and flexible tool.