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min
, max
, and minmax
should be constexpr
Section: 27.8.9 [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.
In 27.1 [algorithms.general], header <algorithm>
synopsis, and 27.8.9 [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);