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Section: 24.4 [associative] Status: NAD Concepts Submitter: Alisdair Meredith Opened: 2009-04-29 Last modified: 2016-01-28
Priority: Not Prioritized
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View all issues with NAD Concepts status.
Discussion:
According to table 87 (n2857) the expression X::key_equal
for an unordered
container shall return a value of type Pred
, where Pred
is an equivalence
relation.
However, all 4 containers constrain Pred
to be merely a Predicate
,
and not EquivalenceRelation
.
[ Batavia (2009-05): ]
We agree with the proposed resolution.
Move to Review.
Proposed resolution:
For ordered containers, replace
Predicate<auto, Key, Key> Compare = less<Key>
with
StrictWeakOrder<auto, Key, Key> Compare = less<Key>
For unordered containers, replace
Predicate<auto, Key, Key> Compare = less<Key>
with
EquivalenceRelation<auto, Key, Key> Compare = less<Key>
As in the following declarations:
Associative containers 24.4 [associative]
1 Headers
<map>
and<set>
:Header
<map>
synopsisnamespace std { template <ValueType Key, ValueType T,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class map; ... template <ValueType Key, ValueType T,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class multimap; ... }Header <set> synopsis
namespace std { template <ValueType Key,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<Key> > requires NothrowDestructible<Key> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class set; ... template <ValueType Key,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<Key> > requires NothrowDestructible<Key> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class multiset; ... }23.4.1p2 Class template map [map]
namespace std { template <ValueType Key, ValueType T,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class map { ... }; }23.4.2p2 Class template multimap [multimap]
namespace std { template <ValueType Key, ValueType T,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class multimap { ... }; }23.4.3p2 Class template set [set]
namespace std { template <ValueType Key,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<Key> > requires NothrowDestructible<Key> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class set { ... }; }23.4.4p2 Class template multiset [multiset]
namespace std { template <ValueType Key,PredicateStrictWeakOrder<auto, Key, Key> Compare = less<Key>, Allocator Alloc = allocator<Key> > requires NothrowDestructible<Key> && CopyConstructible<Compare> && AllocatableElement<Alloc, Compare, const Compare&> && AllocatableElement<Alloc, Compare, Compare&&> class multiset { ... }; }23.5 Unordered associative containers [unord]
1 Headers <unordered_map> and <unordered_set>:
Header <unordered_map> synopsis
namespace std { // 23.5.1, class template unordered_map: template <ValueType Key, ValueType T, Callable<auto, const Key&> Hash = hash<Key>,PredicateEquivalenceRelation<auto, Key, Key> Pred = equal_to<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_map; // 23.5.2, class template unordered_multimap: template <ValueType Key, ValueType T, Callable<auto, const Key&> Hash = hash<Key>,PredicateEquivalenceRelation<auto, Key, Key> Pred = equal_to<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_multimap; ... }Header <unordered_set> synopsis
namespace std { // 23.5.3, class template unordered_set: template <ValueType Value, Callable<auto, const Value&> Hash = hash<Value>,PredicateEquivalenceRelation<auto, Value, Value> class Pred = equal_to<Value>, Allocator Alloc = allocator<Value> > requires NothrowDestructible<Value> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_set; // 23.5.4, class template unordered_multiset: template <ValueType Value, Callable<auto, const Value&> Hash = hash<Value>,PredicateEquivalenceRelation<auto, Value, Value> class Pred = equal_to<Value>, Allocator Alloc = allocator<Value> > requires NothrowDestructible<Value> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_multiset; ... }23.5.1p3 Class template unordered_map [unord.map]
namespace std { template <ValueType Key, ValueType T, Callable<auto, const Key&> Hash = hash<Key>,PredicateEquivalenceRelation<auto, Key, Key> Pred = equal_to<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_map { ... }; }23.5.2p3 Class template unordered_multimap [unord.multimap]
namespace std { template <ValueType Key, ValueType T, Callable<auto, const Key&> Hash = hash<Key>,PredicateEquivalenceRelation<auto, Key, Key> Pred = equal_to<Key>, Allocator Alloc = allocator<pair<const Key, T> > > requires NothrowDestructible<Key> && NothrowDestructible<T> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_multimap { ... }; }23.5.3p3 Class template unordered_set [unord.set]
namespace std { template <ValueType Value, Callable<auto, const Value&> Hash = hash<Value>,PredicateEquivalenceRelation<auto, Value, Value> class Pred = equal_to<Value>, Allocator Alloc = allocator<Value> > requires NothrowDestructible<Value> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_set { ... }; }23.5.4p3 Class template unordered_multiset [unord.multiset]
namespace std { template <ValueType Value, Callable<auto, const Value&> Hash = hash<Value>,PredicateEquivalenceRelation<auto, Value, Value> class Pred = equal_to<Value>, Allocator Alloc = allocator<Value> > requires NothrowDestructible<Value> && SameType<Hash::result_type, size_t> && CopyConstructible<Hash> && CopyConstructible<Pred> && AllocatableElement<Alloc, Pred, const Pred&> && AllocatableElement<Alloc, Pred, Pred&&> && AllocatableElement<Alloc, Hash, const Hash&> && AllocatableElement<Alloc, Hash, Hash&&> class unordered_multiset { ... }; }