为什么std :: bitset :: size是非静态的 [英] Why is std::bitset::size non-static

问题描述

我不能想象为什么选择 std :: bitset :: size 是非静态的。这使得很难得到 constexpr size;你必须这样写：

I can't possibly imagine why it was chose that std::bitset::size is non-static. It makes it much harder to get a constexpr size; you have to write something like this:

template<int val>
struct int_
{
   static const constexpr value = val;
};

template<size_t size>
auto getBitsetSizeIMPL(std::bitset<size>)
{
   return int_<size>{};
}

template<typename BitsetType>
constexpr size_t getBitsetSize()
{
    return decltype(getBitsetSizeIMPL(BitsetType{}))::value;
}

如果它是静态的，你必须做的是

When if it were static all you would have to do would be

BitsetType::size()

b $ b

并且不会牺牲功能。

and there would be no sacrifice of functionality.

有没有历史原因，我缺少或有一个技术事实，我失踪？ / p>

Is there a historical reason that I am missing or is there a technical fact I am missing?

推荐答案

假设不是 constexpr std :: bitset :: size 不正确：

The assumption of a not constexpr std::bitset::size is incorrect:

std::size_t size() const; // until C++11
constexpr std::size_t size();  // since C++11, until C++14
constexpr std::size_t size() const; // since C++14)

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