Associativity of fold-expressions
问题 N4191 proposed fold-expressions to C++. The definition there was that (args + ...) is a left-fold (i.e. (((a0 + a1) + a2) + ...) , and that (... + args) is a right-fold (i.e. (... + (a8 + (a9 + a10))) . However, the revised paper N4295 reversed the definitions of left and right unary folds. Question : what is the rationale? It seems more intuitive (at least when you are used to left-to-right alphabets) to evaluate (args + ...) from left-to-right. 回答1: From the comment by @cpplearner, here's