# deduction guides for std::forward_list

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

This deduction guide is provided for forward_list to allow deduction from an iterator range. This overload only participates in overload resolution if InputIt satisfies InputIterator and Alloc satisfies Allocator

Note: the extent to which the library determines that a type does not satisfy InputIterator 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

#include <forward_list>
#include <vector>
int main() {
std::vector<int> v = {1, 2, 3, 4};
std::forward_list x{v.begin(), v.end()}; // uses explicit deduction guide
}