/* Code for exercise 11.21. |  | "C++ Solutions--Companion to The C++ Programming Language, Third Edition" | by David Vandevoorde; Addison-Wesley 1998; ISBN 0-201-30965-3. | | Permission to use, copy, modify, distribute and sell this software | and its documentation for any purpose is hereby granted without fee. | The author makes no representations about the suitability of this | software for any purpose.  It is provided "as is" without express or | implied warranty. `----------------------------------------------------------------------*/#include <stdio.h>#include <math.h>struct Index {   Index(double p): p_(p) {}   Index const& operator*() const { return *this; }   double value() const { return p_; }private:   double p_;};double mypow(double b, Index p) {   return pow(b, p.value());}double operator*(double a, Index const &b) {   return mypow(a, b);}int main() {   printf("2.3**Index(3.0) = %f\n", 2.3**Index(3.0));   return 0;}