CODEWITHSUNDEEP
c++classtemplates
vorogurcov
vorogurcov

Reputation: 3

How to use CONST instead of ENUM in a template class

So I'm trying to implement template class that holds a static array and I would like to use const int size as a parameter but the only way I can implement this class is by using enum technique for creating such an array.

template<class T>
class Stack
{
private:
    const int SIZE = 100;
    T data[SIZE];
public:

};


template<class T>
class StackTemplate {
    enum {ssize = 100};
    T stack[ssize];
    int top;
public:
    
};

The first implementation results in error in contrast to second one which is good. Is there any possible way to implement it using const int?

I get this error "C2597 illegal reference to non-static member 'Stack::SIZE' TheRevision" if I try to use const int instead of enum.

Upvotes: 0

Views: 55

Answers (2)

Pepijn Kramer
Pepijn Kramer

Reputation: 13076

Make the size of your stack a template parameter too like this. (side notd I prefer not to use "C" style arrays)

#include <array>

template<typename T, std::size_t SIZE> // optionally make SIZE have a default value. E.g. std::size_t SIZE=100
class Stack
{
public: 
    constexpr std::size_t size() const noexcept
    {
        return data.size(); // OR return SIZE, but this shows the use of std::array
    }

private:
    std::array<T,SIZE> data;
};

int main()
{
    Stack<int,100> stack;
    static_assert(stack.size() == 100);
}

Upvotes: 1

rustyx
rustyx

Reputation: 85481

The compiler is hinting at a solution: just make SIZE static:

template<class T>
class Stack
{
private:
    static const int SIZE = 100;
    T data[SIZE];
public:

};

Better yet, make it static constexpr int SIZE = 100;

Or, perhaps even better, make SIZE a template argument:

template<class T, size_t SIZE = 100>
class Stack
{
private:
    T data[SIZE];
public:

};

Upvotes: 2

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