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### 2026. `hash` should be `std` qualified for unordered container

Section: 24.5 [unord] Status: NAD Submitter: Pete Becker Opened: 2011-02-07 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

Tom Plum pointed out to me that there's an apparent inconsistency in the `std::` qualification of template names in the unordered containers:

>      template <class Key,
>                class T,
>                class Hash = hash<Key>,
>                class Pred = std::equal_to<Key>,
>                class Alloc = std::allocator<std::pair<const Key, T> > >
>        class unordered_map;

Is there a reason that hash is not qualified with `std::`? TR1 also does not use `std::` here.

[ 2011-02-07 Chris Jefferson adds: ]

I assumed (I might be wrong) it is because `hash` is designed to be a customisation point, like `swap`.

[ 2011-02-07 Howard Hinnant adds: ]

I think this is incorrect. We mean `std::hash`, though clients are free to specialize `std::hash` on user-defined types. With the possible exception of `begin`/`end` (which I'm not sure if we've settled that), `swap` is the only intended customization point (look up a function by ADL) in the `std::` lib.

[ 2011-02-24 Chris Jefferson adds: ]

I recommend NAD, due to 16.4.2.2 [contents] p3:

> Whenever a name `x` defined in the standard library is mentioned, the name `x` is assumed to be fully qualified as `::std::x`, unless explicitly described otherwise. For example, if the Effects section for library function `F` is described as calling library function `G`, the function `::std::G` is meant.

[2011-02-25 Reflector discussion]

Moved to Tentatively NAD after 5 votes.

Proposed resolution: