Calculate some values using template size_t param

Question

What is the C++ way to calculate some values using template params?

template<typename T, size_t SIZE>
class ThreadSafeArray
{
private:
    static const size_t BLOCK_SIZE = SIZE > 32 ? 16 : 4;
    static const size_t MUTEX_COUNT = SIZE / BLOCK_SIZE + 1;
    ...
};

or this

template<typename T, size_t SIZE>
class ThreadSafeArray
{
private:
    enum
    {
        BLOCK_SIZE = SIZE > 32 ? 16 : 4,
        MUTEX_COUNT = SIZE / BLOCK_SIZE + 1
    };
        ....
};

or somehow else?

In C++, as in most other languages, there is no "one correct way" of doing things. — Some programmer dude, Jul 23 '13 at 06:35
I agree with you, both these ways are correct, but I want to know some good practices in this subject — Evgeny Eltishev, Jul 23 '13 at 06:40

score 2 · Accepted Answer · edited May 23 '17 at 12:21

2

The enum hack is the old way to provide compile-time computations. It was used when in class initialization is not supportted by some compilers, so static const cannot be used. Nowadays its fixed in all modern compilers. So the preferred way is to use static const.

Check this answer for more info.

edited May 23 '17 at 12:21

Community

1
1

answered Jul 23 '13 at 06:41

Manu343726

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score 1 · Answer 2 · answered Jul 23 '13 at 06:40

1

The "enum hack" works with really old compilers that don't implement static const correctly (mostly pre-standard ones).

Unless you have no choice but to develop for such ancient tools, the static const version is clearly preferable.

answered Jul 23 '13 at 06:40

Jerry Coffin

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Calculate some values using template size_t param

2 Answers2