deduction guides for std::{{{1}}}

 

C++

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array (C++11)

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unordered_set (C++11)

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stack

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flat_multimap (C++23)

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span (C++20)

mdspan (C++23)

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template< class InputIt,           class Alloc = std::allocator<typename std::iterator_traits<InputIt>::value_type>> {{{1}}}( InputIt, InputIt, Alloc = Alloc() )   -> {{{1}}}<typename std::iterator_traits<InputIt>::value_type, Alloc>;	(1)	(since C++17)
template< ranges::input_range R,           class Alloc = std::allocator<ranges::range_value_t<R>> > {{{1}}}( std::from_range_t, R&&, Alloc = Alloc() )   -> {{{1}}}<ranges::range_value_t<R>, Alloc>;	(2)	(since C++23)

1) This deduction guide is provided for {{{1}}} to allow deduction from an iterator range. This overload participates in overload resolution only if InputIt satisfies LegacyInputIterator and Alloc satisfies Allocator.

2) This deduction guide is provided for {{{1}}} to allow deduction from a std::from_range_t tag and an input_range.

Note: the extent to which the library determines that a type does not satisfy LegacyInputIterator is unspecified, except that as a minimum integral types do not qualify as input iterators. Likewise, the extent to which it determines that a type does not satisfy Allocator is unspecified, except that as a minimum the member type Alloc::value_type must exist and the expression std::declval<Alloc&>().allocate(std::size_t{}) must be well-formed when treated as an unevaluated operand.

Example

Run this code

#include <{{{1}}}>
#include <vector>
int main() {
    std::vector<int> v = {1, 2, 3, 4};
 
    // uses explicit deduction guide to deduce std::{{{1}}}<int>
    std::{{{1}}} x(v.begin(), v.end()); 
 
    // deduces std::{{{1}}}<std::vector<int>::iterator>
    // first phase of overload resolution for list-initialization selects the candidate
    // synthesized from the initializer-list constructor; second phase is not performed and
    // deduction guide has no effect
    std::{{{1}}} y{v.begin(), v.end()};
}