C++ - упражнение #2

namespace Example2_ConstructorVsCast
{
	namespace Intro1 // practice implicit cast with constructor
	{
		class A {};
		class B { public: B(const A&){} }; // A->B conversion

		void getB(const B&) {}

		void trivial()
		{
			A a;
			getB(a); // 'a' is implicitly casted to B with user-defined conversion (constructor)
		}
	}
	namespace Intro2 // practive implicit cast to derived class and then implicit built-in cast to base type reference!
	{
		class C;
		class A { public: operator C(); }; // A->C conversion

		class B {};
		class C : public B {  };

		void getB(const B&) {}
		A::operator C() { return C(); }

		void almostTrivial1()
		{
			A a;
			getB(a);  // do you know this works?
		}

		class A1 {};
	    class C1 : public B { C1(const A1 &) {} }; // A1->C1 conversion

	    void almostTrivial2()
	    {
#if 0
	    	A1 a1;
	    	getB(a1); // and this does not!
#endif
	    }
	}
	namespace Now // let's have both of them
	{
		class C;
		class A {public: operator C(); }; // A->C conversion
		class B {
			public:
			B() { }
			B(const A&){} // A->B conversion
		};
		class C : public B {  };

		A::operator C() { return C(); }

		void getB(const B&) {}

		void almostTrivial()
		{
			A a;
			getB(a); // which of two conversions is called?
		}
	}
}