More C++ Idioms/Guidelines

Guidelines

 * By their nature, idioms tend to have appeared in the C++ community and in published work many times. An effort should be made to refer to the original source(s) where possible. If you find a reference incomplete or incorrect, please suggest improvements.
 * Please make sure that the code snippets compile on at least 2 major compilers with minimal efforts.
 * If you find code that does not compile, please report.