// operator[] moet twee maal gedefinieerd worden



#include <iostream>

#include <cassert>

using namespace std;



/*

	overloaden van operator[] ...



	je moet altijd twee memberfuncties definieren zodat de operator[] werkt 

	met const objecten en ook met non-const objecten:



	T& operator[](int);              // called for non-const object

	const T& operator[](int) const;  // called for const object



	Array5  is niet correct

	Array6	is niet correct

	Array10 is wel correct

*/



class Array5 {

public:

	Array5();

	int& operator[](int index) const;

private:

	int data[5];

};



Array5::Array5() {

	for (int i(0); i<5; ++i)

		data[i]=0;

}



int& Array5::operator[](int index) const {

	assert(index<5);

//	return data[index];

//	[C++ Error (Borland)]:   Reference initialized with 'const int', needs lvalue of type 'int'

//	[C++ Error (Microsoft)]: 'return' : cannot convert from 'const int' to 'int &' (Conversion loses qualifiers)

//	[C++ Error (gcc)]:       invalid initialization of reference of type 'int &' from expression of type 'const int'

//	de compiler herkend de fout!

//	We kunnen daar wel om heen werken, maar dan kun je ook in een const

//	Array5 schrijven en dat is niet de bedoeling:

	return (int&)(data[index]);

}



class Array6 {

public:

	Array6();

	int& operator[](int index);

private:

	int data[6];

};



Array6::Array6() {

	for (int i(0); i<6; ++i)

		data[i]=0;

}



int& Array6::operator[](int index) {

	assert(index<6);

	return data[index];

}



class Array10 {

public:

	Array10();

	int& operator[](int index);

	const int& operator[](int index) const;

private:

	int data[10];

};



Array10::Array10() {

	for (int i(0); i<10; ++i)

		data[i]=0;

}



int& Array10::operator[](int index) {

	assert(index<10);

	return data[index];

}



const int& Array10::operator[](int index) const {

	assert(index<10);

	return data[index];

}



int main() {

	Array5 v5;

	for (int i(0); i<5; ++i)

		v5[i]=i;

	const Array5 w5(v5);

	w5[0]=5;

//	Schrijven in een const Array moet niet mogen maar mag hier wel!

	for (int i(0); i<5; ++i)

		cout<<v5[i];

	cout<<endl;

	for (int i(0); i<5; ++i)

		cout<<w5[i];

	cout<<endl;



	Array6 v6;

	for (int j(0) ;j<6; ++j)

		v6[j]=j;

	const Array6 w6(v6);

//	w6[0]=6;

//	[C++ Error (Borland)]:   'operator+' not implemented in type 'Array6' for arguments of type 'int'

//	Vreemde foutmelding!

//	[C++ Error (Microsoft)]: binary '[' : no operator found which takes a left-hand operand of type 'const Array6' (or there is no acceptable conversion)

//	Betere foutmelding.

//	[C++ Error (gcc)]:       no match for 'operator[]' in 'w6[0]'

//	Beste foutmelding.

	for (int j(0); j<6; ++j)

		cout<<v6[j];

	cout<<endl;

//	for (int j(0); j<6; ++j)

//		cout<<w6[j];

//	[C++ Error (Borland)]:   'operator+' not implemented in type 'Array6' for arguments of type 'int'

//	Vreemde foutmelding!

//	[C++ Error (Microsoft)]: binary '[' : no operator found which takes a left-hand operand of type 'const Array6' (or there is no acceptable conversion)

//	Betere foutmelding.

//	[C++ Error (gcc)]:       no match for 'operator[]' in 'w6[j]'

//	Beste foutmelding.

//	Lezen uit een const Array moet wel mogen maar mag hier niet!

	cout<<endl;



	Array10 v10;

	for (int k(0); k<10; ++k)

		v10[k]=k;

	const Array10 w10(v10);

//	w10[0]=10;

//	[C++ Error (Borland)]:   Cannot modify a const object

//	[C++ Error (Microsoft)]: 'w10' : you cannot assign to a variable that is const

//	[C++ Error (gcc)]:       assignment of read-only location

	for (int k(0); k<10; ++k)

		cout<<v10[k];

	cout<<endl;

	for (int k(0); k<10; ++k)

		cout<<w10[k];

	cout<<endl;



	cin.get();

	return 0;

}