"Thinkinginc++" 40, on the effect of const on function return value

Whenever you pass an address to a function, you should modify it as const as you can .

/*** book: "thinkinginc++" * function: On the role of const on function return value * Time: September 7, 2014 14:14:57* Author: cutter_point*/class x{    int i;public:    X (int ii=0);    void modify ();}; x::x (int ii) {    i=ii;} void X::modify () {    i++;} X f5 () {    return x ();//An object, the default constructor, returns an lvalue that can be assigned to modify}const x f6 () {    return x ();//return the const type of}void F7 (x& X) { C10/>x.modify ();} int main () {    F5 () =x (1);    F5 (). modify ();    //! F7 (F5 ());   Here is the reference, C + + cannot be compiled by the reason that parameter passing will establish a replica    //! f6 () =x (1);  Returns a const type that cannot change the value of    //! f6 (). modify ();    //! F7 (f6 ());   Here the argument is a reference, not a const reference to    return 0;}

"Thinkinginc++" 40, on the effect of const on function return value