"要想定义成c o n s t e x p r ,函数必须非常简单:函数中仅有一条计算某个值的r e t u r n语句。c o n s t e x p r函数可以接受非常量实参,但此时其结果不再是一个常量表达式。当程序的上下文不需要常量表达式时,我们可以使用非常量实参来调用c on s t e x p r函数,这样我们就不用把同一个函数定义两次了:其中一个用于常量表达式,另一个用于变量。"
"我打断你的时候不许打断我"
"能在浪费时间中获得乐趣,就不是浪费时间。 一 伯特兰· 罗素"
"The central language feature of C++ is the class. A class is a user-defined type provided t represent a concept in the code of a program. Whenever our design for a program has a useful concept, idea, entity, etc, we try to represent it as a class in the program so that the idea is there in the code,"