What is the implementation of std::min() that has a single parameter?

Question

I saw the following statement in a code:

std::min(0);

The closest definition I can find is:

template <class T> constexpr T min (initializer_list<T> il);

So far I found the implementation in stl_algo.h:

template<typename _Tp>
    _GLIBCXX14_CONSTEXPR
    inline _Tp
    min(initializer_list<_Tp> __l)
    { return *std::min_element(__l.begin(), __l.end()); }

I used to think that std::min() only calculates the minimum of two items. Can anyone explain to me what does it actually do? And what is an initializer_list?

Answer 1

To answer the question in your title, the minimum of a set of numbers when the set contains one number is the number itself. That's easy for me to understand. I hope it is for you to understand too.

I used to think that std::min() only calculates the minimum of two items.

It used to be but since C++11, it has changed. Since C++11, there is

template< class T >
T min( std::initializer_list<T> ilist );

and a few variants. It can be used as:

std::min({num1, num2, ..., numn});

I am surprised that

std::min(0);

works for you. It should not. Perhaps it is supported by g++ as a non-standard extension. However, you should be able to use

std::min({0}); // That becomes an intializer_list<int> with one item.

That is standards compliant.