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### 2350. `min`, `max`, and `minmax` should be `constexpr`

Section: 25.8.9 [alg.min.max] Status: C++14 Submitter: Ville Voutilainen Opened: 2013-12-15 Last modified: 2016-01-28

Priority: 1

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Discussion:

Having `min`, `max`, and `minmax` `constexpr` was a large part of the motivation to allow reference-to-const arguments for `constexpr` functions as per N3039. Furthermore, `initializer_lists` are immutable and not-movable-from for large part in order to allow using them in `constexpr` contexts and other hoisting-optimizations. In N3797 version of the draft none of these functions are `constexpr`, and they should be made `constexpr`.

Proposed resolution:

This wording is relative to N3797.

1. In 25.1 [algorithms.general], header `<algorithm>` synopsis, and 25.8.9 [alg.min.max], change as indicated (add `constexpr` to every signature before `min_element`):

   >     template<class T> constexpr const T& min(const T& a, const T& b);
   >     template<class T, class Compare>
   >     constexpr const T& min(const T& a, const T& b, Compare comp);
   >     […]
   >     template<class T>
   >     constexpr T min(initializer_list<T> t);
   >     template<class T, class Compare>
   >     constexpr T min(initializer_list<T> t, Compare comp);
   >     […]
   >     template<class T> constexpr const T& max(const T& a, const T& b);
   >     template<class T, class Compare>
   >     constexpr const T& max(const T& a, const T& b, Compare comp);
   >     […]
   >     template<class T>
   >     constexpr T max(initializer_list<T> t);
   >     template<class T, class Compare>
   >     constexpr T max(initializer_list<T> t, Compare comp);
   >     […]
   >     template<class T> constexpr pair<const T&, const T&> minmax(const T& a, const T& b);
   >     template<class T, class Compare>
   >     constexpr pair<const T&, const T&> minmax(const T& a, const T& b, Compare comp);
   >     […]
   >     template<class T>
   >     constexpr pair<T, T> minmax(initializer_list<T> t);
   >     template<class T, class Compare>
   >     constexpr pair<T, T> minmax(initializer_list<T> t, Compare comp);