P0458R2 Checking for Existence of an Element in Associative Containers

[associative.reqmts] Add "contains" to the list of member function
templates that do not participate in overload resolution unless the
comparator is transparent, as agreed on the lib reflector.

Author: jwakely

source/containers.tex

@@ -1620,6 +1620,15 @@
 \tcode{m} denotes an allocator of a type convertible to \tcode{A},
 and \tcode{nh} denotes a non-const rvalue of type \tcode{X::node_type}.
 
+% Local command to index names as members of all ordered containers.
+\newcommand{\indexordmem}[1]{%
+\indexlibrary{\idxcode{#1}!ordered associative containers}%
+\indexlibrary{\idxcode{set}!\idxcode{#1}}%
+\indexlibrary{\idxcode{map}!\idxcode{#1}}%
+\indexlibrary{\idxcode{multiset}!\idxcode{#1}}%
+\indexlibrary{\idxcode{multimap}!\idxcode{#1}}%
+}
+
 \begin{libreqtab4b}
 {Associative container requirements (in addition to container)}
 {tab:containers.associative.requirements}
@@ -1948,6 +1957,19 @@
  \tcode{!c(r, ke) \&\& !c(ke, r)}    &
  $\log (\tcode{a_tran.size()}) + \tcode{a_tran.count(ke)}$   \\ \rowsep
 
+\indexordmem{contains}%
+\tcode{b.}\br
+ \tcode{contains(k)}  &
+ \tcode{bool}         &
+ equivalent to \tcode{b.find(k) != b.end()}  &
+ logarithmic            \\ \rowsep
+
+\tcode{a_tran.}\br
+ \tcode{con\-tains(ke)} &
+ \tcode{bool}         &
+ equivalent to \tcode{a_tran.find(ke) != a_tran.end()}  &
+ logarithmic            \\ \rowsep
+
 \tcode{b.lower_bound(k)}   &
  \tcode{iterator}; \tcode{const_iterator} for constant \tcode{b}.  &
  returns an iterator pointing to the first element with
@@ -2044,9 +2066,11 @@
 its constructor.
 
 \pnum
-The member function templates \tcode{find}, \tcode{count}, \tcode{lower_bound},
-\tcode{upper_bound}, and \tcode{equal_range} shall not participate in overload
-resolution unless the \grammarterm{qualified-id} \tcode{Compare::is_transparent} is valid
+The member function templates
+\tcode{find}, \tcode{count}, \tcode{contains},
+\tcode{lower_bound}, \tcode{upper_bound}, and \tcode{equal_range}
+shall not participate in overload resolution unless
+the \grammarterm{qualified-id} \tcode{Compare::is_transparent} is valid
 and denotes a type\iref{temp.deduct}.
 
 \pnum
@@ -2672,6 +2696,13 @@
 &   Average case \bigoh{\tcode{b.count(k)}}, worst case \bigoh{\tcode{b.size()}}.
 \\ \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
+%
 \indexunordmem{equal_range}%
 \tcode{b.equal_range(k)}
 &   \tcode{pair<iterator, iterator>}; \br
@@ -6104,6 +6135,9 @@
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
 
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
+
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
@@ -6596,6 +6630,9 @@
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
 
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
+
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
@@ -6875,6 +6912,9 @@
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
 
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
+
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
@@ -7126,6 +7166,9 @@
     size_type      count(const key_type& x) const;
     template<class K> size_type count(const K& x) const;
 
+    bool           contains(const key_type& x) const;
+    template<class K> bool contains(const K& x) const;
+
     iterator       lower_bound(const key_type& x);
     const_iterator lower_bound(const key_type& x) const;
     template<class K> iterator       lower_bound(const K& x);
@@ -7536,6 +7579,7 @@
     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;
 
@@ -8064,6 +8108,7 @@
     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;
 
@@ -8390,6 +8435,7 @@
     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;
 
@@ -8678,6 +8724,7 @@
     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;