NAME¶

deductionguidesforstd::forward_list - deductionguidesforstd::forward_list

Synopsis¶

Defined in header <forward_list>
template< class InputIt,

class Alloc = std::allocator<typename
std::iterator_traits<InputIt>::value_type>> (since C++17)
forward_list(InputIt, InputIt, Alloc = Alloc())

-> forward_list<typename std::iterator_traits<InputIt>::value_type,
Alloc>;

This deduction guide is provided for forward_list to allow deduction from an
iterator range. This overload participates in overload resolution only 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 <forward_list>
#include <vector>
int main() {
std::vector<int> v = {1, 2, 3, 4};

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

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