/* Code for exercise 11.1. |  | "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 <iostream>struct X {   int I;   X() {}   X(int i): I(i) { std::cerr << "X::X(int)\n"; }   X operator+(int i) {      std::cerr << "X::operator+(int)\n";      X r;      r.I = I+i;      return r;   }};struct Y {   int I;   Y() {}   Y(X x): I(x.I) { std::cerr << "Y::Y(X)\n"; }   Y operator+(X x) {      Y r;      r.I = I+x.I;      return r;   }   operator int() { std::cerr << "Y::operator int()\n"; return I; }};extern X operator*(X x, Y y) {   X r;   r.I = x.I+y.I;   return r;}extern int f(X x) {   return x.I;}X x = 1;Y y = x;int i = 2;int main() {   cout << "i+10 = ... " << i+10 << '\n' << std::endl; // No conversion needed#if defined COMPILE_ERRORS   y+10; // Error: ambiguous!      // y.operator int()+10 or y+X(10)   y+10*y; // Error: ambiguous again!      // y+X(10*y.operator int()) or y+X(10)*y#endif	std::cout << "x+y+i = ... " << (x+y+i).I << '\n' << std::endl;#if 0   (x+y.operator int())+i; // Uses X::operator+(int) twice;                           // result has type X#endif   std::cout << "x*x+i = ... " << (x*x+i).I << '\n' << std::endl;#if 0   x*Y(x)+X(i); // Result has type X#endif   std::cout << "f(7) = ... " << f(7) << '\n' << std::endl;#if 0   f(X(7));#endif#if defined COMPILE_ERRORS   f(y); // Error: no valid implicit conversion from Y to X#endif   std::cout << "y+y = ... " << y+y << '\n' << std::endl;#if 0   y.operator int()+y.operator int(); // Result has type int#endif   std::cout << "106+y = ... " << 106+y << '\n' << std::endl;#if 0   106+y.operator int(); // Result has type int#endif};