TIL: never depend on the order of evaluation of sub-expressions in a stream

The code below may result in a 6 different execution orders. It will surprise and hurt you, so don't do that ;-)

std::cout << wizard.CastSpell("abracadabra") << wizard.DrinkPotion("Rosanke") << wizard.Mana();

More info can be found:

• http://stackoverflow.com/questions/14809978/order-of-execution-in-operator
• EXP10-C. Do not depend on the order of evaluation of subexpressions or the order in which side effects take place