# deduction guides for `std::list`

From cppreference.com
< cpp‎ | container‎ | list

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

This deduction guide is provided for list 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 <list>
    #include <vector>
    int main() {
       std::vector<int> v = {1, 2, 3, 4};

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

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

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