Deduce the specified type t_TYPE from the corresponding template parameter type supplied to the constructor of optional. This guide does not participate in deduction unless the deduced type t_TYPE supports the bslma allocator model, and the specified t_ALLOC can be implicitly converted to bsl::allocator<char>.

Synopsis

Declared in <bslstl_optional.h>

template<
    class t_TYPE,
    class t_ALLOC>
requires BloombergLP::bslma::UsesBslmaAllocator<t_TYPE>::value && bsl::is_convertible_v<t_ALLOC, bsl::allocator<char>>
optional<t_TYPE>(
    std::allocator_arg_t,
    t_ALLOC,
    optional<t_TYPE>) → optional<t_TYPE>;

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