deduction guides for std::optional

< cpp‎ | utility‎ | optional
Defined in header <optional>
template<class T>
optional(T) -> optional<T>;
 (since C++17)

One deduction guide is provided for std::optional to account for the edge cases missed by the implicit deduction guides, in particular, non-copyable arguments and array to pointer conversion

Example

#include <optional>
 
int main()
{
    int a[2];
    std::optional oa{a}; // explicit deduction guide is used in this case
}