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P0919R3 Heterogeneous lookup for unordered containers #2479

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5c08155
P0919R3 Heterogeneous lookup for unordered containers
Nov 16, 2018
38f9dcc
[unord.req] Use bullets for the list of denoting variables.
Nov 16, 2018
e6bbbbf
[unord.req] Clarify what r1 is and remove unnecessary variable e.
zygoloid Nov 26, 2018
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227 changes: 174 additions & 53 deletions source/containers.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -2177,9 +2177,10 @@

\pnum
\indextext{unordered associative containers!equality function}%
Two values \tcode{k1} and \tcode{k2} of type \tcode{Key} are
Two values \tcode{k1} and \tcode{k2} are
considered equivalent if the container's
key equality predicate returns
key equality predicate
\tcode{pred(k1, k2)} is valid and returns
\tcode{true} when passed those values. If \tcode{k1} and
\tcode{k2} are equivalent, the container's hash function shall
return the same value for both.
Expand Down Expand Up @@ -2256,27 +2257,43 @@
\indextext{unordered associative containers!equivalent keys}%
\indextext{requirements!container}%
In \tref{HashRequirements}:
\tcode{X} denotes an unordered associative container class,
\tcode{a} denotes a value of type \tcode{X},
\tcode{a2} denotes a value of a type with nodes compatible with type
\tcode{X} (\tref{containers.node.compat}),
\tcode{b} denotes a possibly const value of type \tcode{X},
\tcode{a_uniq} denotes a value of type \tcode{X} when \tcode{X} supports unique keys,
\tcode{a_eq} denotes a value of type \tcode{X} when \tcode{X} supports equivalent keys,
\tcode{i} and \tcode{j} denote input iterators that refer to \tcode{value_type},
\tcode{[i, j)} denotes a valid range,
\tcode{p} and \tcode{q2} denote valid constant iterators to \tcode{a},
\tcode{q} and \tcode{q1} denote valid dereferenceable constant iterators to \tcode{a},
\tcode{r} denotes a valid dereferenceable iterator to \tcode{a},
\tcode{[q1, q2)} denotes a valid range in \tcode{a},
\tcode{il} denotes a value of type \tcode{initializer_list<value_type>},
\tcode{t} denotes a value of type \tcode{X::value_type},
\tcode{k} denotes a value of type \tcode{key_type},
\tcode{hf} denotes a possibly const value of type \tcode{hasher},
\tcode{eq} denotes a possibly const value of type \tcode{key_equal},
\tcode{n} denotes a value of type \tcode{size_type},
\tcode{z} denotes a value of type \tcode{float},
and \tcode{nh} denotes a non-const rvalue of type \tcode{X::node_type}.
\begin{itemize}
\item \tcode{X} denotes an unordered associative container class,
\item \tcode{a} denotes a value of type \tcode{X},
\item \tcode{a2} denotes a value of a type with nodes compatible
with type \tcode{X} (\tref{containers.node.compat}),
\item \tcode{b} denotes a possibly const value of type \tcode{X},
\item \tcode{a_uniq} denotes a value of type \tcode{X}
when \tcode{X} supports unique keys,
\item \tcode{a_eq} denotes a value of type \tcode{X}
when \tcode{X} supports equivalent keys,
\item \tcode{a_tran} denotes a possibly const value of type \tcode{X}
when the \grammarterm{qualified-id} \tcode{X::hasher::transparent_key_equal}
is valid and denotes a type\iref{temp.deduct},
\item \tcode{i} and \tcode{j} denote input iterators
that refer to \tcode{value_type},
\item \tcode{[i, j)} denotes a valid range,
\item \tcode{p} and \tcode{q2} denote valid constant iterators to \tcode{a},
\item \tcode{q} and \tcode{q1} denote
valid dereferenceable constant iterators to \tcode{a},
\item \tcode{r} denotes a valid dereferenceable iterator to \tcode{a},
\item \tcode{[q1, q2)} denotes a valid range in \tcode{a},
\item \tcode{il} denotes a value of type \tcode{initializer_list<value_type>},
\item \tcode{t} denotes a value of type \tcode{X::value_type},
\item \tcode{k} denotes a value of type \tcode{key_type},
\item \tcode{hf} denotes a possibly const value of type \tcode{hasher},
\item \tcode{eq} denotes a possibly const value of type \tcode{key_equal},
\item \tcode{ke} is a value such that
\begin{itemize}
\item \tcode{eq(r1, ke) == eq(ke, r1)}
\item \tcode{hf(r1) == hf(ke)} if \tcode{eq(r1, ke)} is \tcode{true}, and
\item \tcode{(eq(r1, ke) \&\& eq(r1, r2)) == eq(r2, ke)}
\end{itemize}
where \tcode{r1} and \tcode{r2} are keys of elements in \tcode{a_tran},
\item \tcode{n} denotes a value of type \tcode{size_type},
\item \tcode{z} denotes a value of type \tcode{float}, and
\item \tcode{nh} denotes a non-const rvalue of type \tcode{X::node_type}.
\end{itemize}

% Local command to index names as members of all unordered containers.
\newcommand{\indexunordmem}[1]{%
Expand All @@ -2302,7 +2319,10 @@
%%
\indexunordmem{key_type}%
\tcode{X::key_type} &
\tcode{Key} &
\tcode{Hash::transparent_key_equal}
if such a \grammarterm{qualified-id}
is valid and denotes a type\iref{temp.deduct};
otherwise, \tcode{Pred}. &
&
compile time \\ \rowsep

Expand Down Expand Up @@ -2333,7 +2353,9 @@
%
\indexunordmem{key_equal}%
\tcode{X::key_equal}
& \tcode{Pred}
& \tcode{Hash::transparent_key_equal} if such a \grammarterm{qualified-id}
is valid and denotes a type\iref{temp.deduct};
otherwise, \tcode{Pred}.
& \requires\ \tcode{Pred} is \oldconcept{CopyConstructible}.\br
\tcode{Pred} shall be a binary predicate that takes two arguments
of type \tcode{Key}. \tcode{Pred} is an equivalence relation.%
Expand Down Expand Up @@ -2727,20 +2749,43 @@
& Average case \bigoh{1}, worst case \bigoh{\tcode{b.size()}}.
\\ \rowsep
%
\tcode{a_tran.find(ke)}
& \tcode{iterator}; \br \tcode{const_iterator} for const \tcode{a_tran}.
& Returns an iterator pointing to an element with key equivalent to
\tcode{ke}, or \tcode{a_tran.end()} if no such element exists.%
& Average case \bigoh{1},
worst case \bigoh{\tcode{a_tran.}\br{}\tcode{size()}}. % avoid wverfull
\\ \rowsep
%
\indexunordmem{count}%
\tcode{b.count(k)}
& \tcode{size_type}
& Returns the number of elements with key equivalent to \tcode{k}.%
& Average case \bigoh{\tcode{b.count(k)}}, worst case \bigoh{\tcode{b.size()}}.
\\ \rowsep
%
\tcode{a_tran.count(ke)}
& \tcode{size_type}
& Returns the number of elements with key equivalent to \tcode{ke}.%
& Average case
\bigoh{\tcode{a_tran.}\br{}\tcode{count(ke)}}, % avoid overfull
worst case \bigoh{\tcode{a_tran.}\br{}\tcode{size()}}. % avoid overfull
\\ \rowsep
%
\indexunordmem{contains}%
\tcode{b.contains(k)}
& \tcode{bool}
& Equivalent to \tcode{b.find(k) != b.end()}%
& Average case \bigoh{1}, worst case \bigoh{\tcode{b.size()}}.
\\ \rowsep
%
\tcode{a_tran.contains(ke)}
& \tcode{bool}
& Equivalent to \tcode{a_tran.find(ke) != a_tran.end()}%
& Average case \bigoh{1},
worst case \bigoh{\tcode{a_tran.}\br{}\tcode{size()}}. % avoid overfull
\\ \rowsep
%
\indexunordmem{equal_range}%
\tcode{b.equal_range(k)}
& \tcode{pair<iterator, iterator>}; \br
Expand All @@ -2752,6 +2797,16 @@
\bigoh{\tcode{b.size()}}.
\\ \rowsep
%
\tcode{a_tran.equal_range(ke)}
& \tcode{pair<iterator, iterator>}; \br
\tcode{pair<const_iterator, const_iterator>} for const \tcode{a_tran}.
& Returns a range containing all elements with keys equivalent to
\tcode{ke}. Returns \tcode{make_pair(a_tran.end(), a_tran.end())} if
no such elements exist.%
& Average case
\bigoh{\tcode{a_tran.}\br{}\tcode{count(ke)}}. % avoid overfull
Worst case \bigoh{\tcode{a_tran.}\br{}\tcode{size()}}. % avoid overfull
\\ \rowsep
\indexunordmem{bucket_count}%
\tcode{b.bucket_count()}
& \tcode{size_type}
Expand Down Expand Up @@ -2930,6 +2985,24 @@
obtained while it is owned by a \tcode{node_type} are invalidated if the
element is successfully inserted.

\pnum
If the \grammarterm{qualified-id} \tcode{Hash::transparent_key_equal}
is valid and denotes a type\iref{temp.deduct},
then the program is ill-formed if either:
\begin{itemize}
\item
\grammarterm{qualified-id} \tcode{Hash::transparent_key_equal::is_transparent}
is not valid or does not denote a type, or
\item
\tcode{Pred} is a different type than \tcode{equal_to<Key>} or
\tcode{Hash::transparent_key_equal}.
\end{itemize}
The member function templates
\tcode{find}, \tcode{count}, \tcode{equal_range}, and \tcode{contains}
shall not participate in overload resolution unless
the \grammarterm{qualified-id} \tcode{Hash::transparent_key_equal}
is valid and denotes a type\iref{temp.deduct}.

\pnum
A deduction guide for an unordered associative container shall not participate in overload resolution
if any of the following are true:
Expand Down Expand Up @@ -7492,7 +7565,7 @@
using mapped_type = T;
using value_type = pair<const Key, T>;
using hasher = Hash;
using key_equal = Pred;
using key_equal = @\seeref{unord.req}@;
using allocator_type = Allocator;
using pointer = typename allocator_traits<Allocator>::pointer;
using const_pointer = typename allocator_traits<Allocator>::const_pointer;
Expand Down Expand Up @@ -7626,12 +7699,24 @@
key_equal key_eq() const;

// map operations
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
size_type count(const key_type& k) const;
bool contains(const key_type& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
template <class K>
iterator find(const K& k);
template <class K>
const_iterator find(const K& k) const;
size_type count(const key_type& k) const;
template <class K>
size_type count(const K& k) const;
bool contains(const key_type& k) const;
template <class K>
bool contains(const K& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
template <class K>
pair<iterator, iterator> equal_range(const K& k);
template <class K>
pair<const_iterator, const_iterator> equal_range(const K& k) const;

// \ref{unord.map.elem}, element access
mapped_type& operator[](const key_type& k);
Expand Down Expand Up @@ -8039,7 +8124,7 @@
using mapped_type = T;
using value_type = pair<const Key, T>;
using hasher = Hash;
using key_equal = Pred;
using key_equal = @\seeref{unord.req}@;
using allocator_type = Allocator;
using pointer = typename allocator_traits<Allocator>::pointer;
using const_pointer = typename allocator_traits<Allocator>::const_pointer;
Expand Down Expand Up @@ -8155,12 +8240,24 @@
key_equal key_eq() const;

// map operations
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
size_type count(const key_type& k) const;
bool contains(const key_type& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
template <class K>
iterator find(const K& k);
template <class K>
const_iterator find(const K& k) const;
size_type count(const key_type& k) const;
template <class K>
size_type count(const K& k) const;
bool contains(const key_type& k) const;
template <class K>
bool contains(const K& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
template <class K>
pair<iterator, iterator> equal_range(const K& k);
template <class K>
pair<const_iterator, const_iterator> equal_range(const K& k) const;

// bucket interface
size_type bucket_count() const noexcept;
Expand Down Expand Up @@ -8367,7 +8464,7 @@
using key_type = Key;
using value_type = Key;
using hasher = Hash;
using key_equal = Pred;
using key_equal = @\seeref{unord.req}@;
using allocator_type = Allocator;
using pointer = typename allocator_traits<Allocator>::pointer;
using const_pointer = typename allocator_traits<Allocator>::const_pointer;
Expand Down Expand Up @@ -8482,12 +8579,24 @@
key_equal key_eq() const;

// set operations
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
size_type count(const key_type& k) const;
bool contains(const key_type& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
template <class K>
iterator find(const K& k);
template <class K>
const_iterator find(const K& k) const;
size_type count(const key_type& k) const;
template <class K>
size_type count(const K& k) const;
bool contains(const key_type& k) const;
template <class K>
bool contains(const K& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
template <class K>
pair<iterator, iterator> equal_range(const K& k);
template <class K>
pair<const_iterator, const_iterator> equal_range(const K& k) const;

// bucket interface
size_type bucket_count() const noexcept;
Expand Down Expand Up @@ -8657,7 +8766,7 @@
using key_type = Key;
using value_type = Key;
using hasher = Hash;
using key_equal = Pred;
using key_equal = @\seeref{unord.req}@;
using allocator_type = Allocator;
using pointer = typename allocator_traits<Allocator>::pointer;
using const_pointer = typename allocator_traits<Allocator>::const_pointer;
Expand Down Expand Up @@ -8771,12 +8880,24 @@
key_equal key_eq() const;

// set operations
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
size_type count(const key_type& k) const;
bool contains(const key_type& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
iterator find(const key_type& k);
const_iterator find(const key_type& k) const;
template <class K>
iterator find(const K& k);
template <class K>
const_iterator find(const K& k) const;
size_type count(const key_type& k) const;
template <class K>
size_type count(const K& k) const;
bool contains(const key_type& k) const;
template <class K>
bool contains(const K& k) const;
pair<iterator, iterator> equal_range(const key_type& k);
pair<const_iterator, const_iterator> equal_range(const key_type& k) const;
template <class K>
pair<iterator, iterator> equal_range(const K& k);
template <class K>
pair<const_iterator, const_iterator> equal_range(const K& k) const;

// bucket interface
size_type bucket_count() const noexcept;
Expand Down
2 changes: 2 additions & 0 deletions source/macros.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -296,6 +296,8 @@
\newcommand{\unspecbool}{\UNSP{unspecified-bool-type}}
\newcommand{\seebelow}{\UNSP{see below}}
\newcommand{\seebelownc}{\UNSPnc{see below}}
\newcommand{\seeref}[1]{\UNSP{see~\ref{#1}}}
\newcommand{\seerefnc}[1]{\UNSPnc{see~\ref{#1}}}
\newcommand{\unspecuniqtype}{\UNSP{unspecified unique type}}
\newcommand{\unspecalloctype}{\UNSP{unspecified allocator type}}

Expand Down
2 changes: 2 additions & 0 deletions source/support.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -596,6 +596,8 @@
\tcode{<numeric>} \\ \rowsep
\defnlibxname{cpp_lib_generic_associative_lookup} & \tcode{201304L} &
\tcode{<map>} \tcode{<set>} \\ \rowsep
\defnlibxname{cpp_lib_generic_unordered_lookup} & \tcode{201811L} &
\tcode{<unordered_map>} \tcode{<unordered_set>} \\ \rowsep
\defnlibxname{cpp_lib_hardware_interference_size} & \tcode{201703L} &
\tcode{<new>} \\ \rowsep
\defnlibxname{cpp_lib_has_unique_object_representations} & \tcode{201606L} &
Expand Down