The lvalue/rvalue metaphor--Joseph Mansfield
Joseph Mansfield discusses about an important topic in C++:
The lvalue/rvalue metaphor
by Joseph Mansfield
From the article:
Every expression in C++ is either an lvalue or an rvalue. This distinction is what makes something like
5 = x;invalid, as the expression 5 is an rvalue expression and so cannot appear on the left of an assignment...

Christophe Riccio gives us an interesting point of view for a library author and shares the latest status of some compilers: