deductionguidesforstdvector(3)

deductionguidesforstd::vector - deductionguidesforstd::vector

Synopsis

Defined in header <vector> template< class InputIt, class Alloc = std::allocator<typename std::iterator_traits<InputIt>::value_type>> (since C++17) vector(InputIt, InputIt, Alloc = Alloc()) -> vector<typename std::iterator_traits<InputIt>::value_type, Alloc>;

This deduction_guide is provided for vector to allow deduction from an iterator range. This overload only participates in overload resolution if InputIt satisfies LegacyInputIterator and Alloc satisfies Allocator. 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 <vector>

int main() { std::vector<int> v = {1, 2, 3, 4};

// uses explicit deduction guide to deduce std::vector<int> std::vector x(v.begin(), v.end());

// deduces std::vector<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::vector y{v.begin(), v.end()}; }