problem with specialized template class with non-type parameter

[learner2009]

I am trying to do a specialized template class of char with non-type parameter. However, it doesn't accept the specialized one and gives error message:

error C2146: syntax error : missing ',' before identifier 'N'

on line 31

Any idea how I can do it? Thanks.

// program testing

#include <iostream>

using namespace std;


// template class Container to contain array of type T with array size N
template <typename T, int N>
class Container {
private:
	T v[N];

public:
	void setMember(int pos, T value);
	T getMember(int n);
};

template <typename T, int N>
void Container<T, N>::setMember(int pos, T value) {
	v[pos] = value;
}

template <typename T, int N>
T Container<T, N>::getMember(int pos) {
	return v[pos];
}


// specialized template class Container to contain array of type char with array size N
template <char, int N>
class Container<char, int N> {
private:
	char v[N];

public:
	void setMember(int pos, char c);
	char getMember(int pos);
	char getUpperMember(int pos);
};

template <char, int N>
void Container<char, int N>::setMember(int pos, char c) {
	v[pos] = value;
}

template <char, int N>
char Container<char, int N>::getMember(int pos) {
	return v[pos];
}

template <char, int N>
char Container<char, int N>::getUpperMember(int pos) {
	return (v[pos] >= 'a' && v[pos] <= 'z')? v[pos] - ('a' - 'A'): v[pos];
}


// mains
int main() {
	Container<int, 10> container1;

	container1.setMember(5, 50);

	cout << container1.getMember(5) << endl;

	return 0;
}

[Gumbercules]

I think

template <char, int N>
void Container<char, int N>::setMember(int pos, char c) 

should just be

template <char, int N>
void Container<char, N>::setMember(int pos, char c) 

but I've never used specialized templates

[learner2009]

Gumbercules, I have tried your suggestion but it gives the following complaint on line 40:

error C3855: 'Container': template parameter 'T' is incompatible with the declaration

[Bazzy]

Try with

template <int N>
void Container<char, N>::setMember(int pos, char c)

[learner2009]

still the error message

syntax error : missing ',' before identifier 'N'

on line 32

[Gumbercules]

it compiled with Bazzy's instruction for me. Check to make sure you didn't miss one.

[learner2009]

tried it. Same original error message. The thing is I have generic template class <typename T, int N> and I am declaring a specialized template class <int N>.

Is this allowed? The program runs if I have only one of them.

[jsmith]

Invert the order of template parameters. N followed by T

You have to default the rightmost one, not the leftmost one, just like default parameters on functions.

[learner2009]

I have tried N followed by T now but it says

error C2975: 'Container' : invalid template argument for 'N', expected compile-time constant expression

on line 32.

I have also tried the type of the specialized one to be <N> and <char, int N> respectively but still doesn't run.

My code now becomes:

#include <iostream>

using namespace std;


// template class Container to contain array of type T with array size N
template <int N, typename T>
class Container {
private:
	T v[N];

public:
	void setMember(int pos, T value);
	T getMember(int n);
};

template <int N, typename T>
void Container<N, T>::setMember(int pos, T value) {
	v[pos] = value;
}

template <int N, typename T>
T Container<N, T>::getMember(int pos) {
	return v[pos];
}


// specialized template class Container to contain array of type char with array size N
template <char, int N>
class Container<char, N> {
private:
	char v[N];

public:
	void setMember(int pos, char c);
	char getMember(int pos);
	char getUpperMember(int pos);
};

template <int N>
void Container<char, int N>::setMember(int pos, char c) {
	v[pos] = value;
}

template <int N>
char Container<char, int N>::getMember(int pos) {
	return v[pos];
}

template <int N>
char Container<char, int N>::getUpperMember(int pos) {
	return (v[pos] >= 'a' && v[pos] <= 'z')? v[pos] - ('a' - 'A'): v[pos];
}


// mains
int main() {
	Container<int, 10> container1;

	container1.setMember(5, 50);

	cout << container1.getMember(5) << endl;

	return 0;
}

Any other suggestion?

[guestgulkan]

My suggestion:

// template class Container to contain array of type T with array size N
template <int N, typename T>
class Container {
private:
	T v[N];

public:
	void setMember(int pos, T value);
	T getMember(int n);
};

template <int N, typename T>
void Container<N, T>::setMember(int pos, T value) {
	v[pos] = value;
}

template <int N, typename T>
T Container<N, T>::getMember(int pos) {
	return v[pos];
}


// specialized template class Container to contain array of type char with array size N
template <int N>
class Container<N, char> {
private:
	char v[N];

public:
	void setMember(int pos, char c);
	char getMember(int pos);
	char getUpperMember(int pos);
};

template <int N>
void Container<N, char>::setMember(int pos, char c) {
	v[pos] = value;
}

template <int N>
char Container<N, char>::getMember(int pos) {
	return v[pos];
}

template <int N>
char Container<N, char>::getUpperMember(int pos) {
	return (v[pos] >= 'a' && v[pos] <= 'z')? v[pos] - ('a' - 'A'): v[pos];
}


// mains
int main() {
	Container<10, int> container1;

	container1.setMember(5, 50);

	cout << container1.getMember(5) << endl;

	return 0;
}