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Difference between revisions of "cpp/named req/ReversibleContainer"

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< cpp‎ | named req
m (Additional fmt; rm "Complexity" column for #Types table (it's compile time by definition for ∀ types))
m (+inplace_vector.)
 
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===Requirements===
 
===Requirements===
 +
A type satisfies {{named req/core|ReversibleContainer}} if it satisfies {{named req|Container}}, its iterator type belongs to the bidirectional or random access [[cpp/iterator|iterator categories]] and, given the following types and values, the semantic and complexity requirements in the tables below are satisfied:
 
{{dsc begin}}
 
{{dsc begin}}
−
{{dsc|{{tt|X}}|Container type}}
+
{{dsc hitem|Type|Definition}}
−
{{dsc|{{tt|T}}|Element type}}
+
{{dsc|{{tt|X}}|an {{named req/core|ReversibleContainer}} type}}
−
{{dsc|{{c|a}}|Objects of type {{tt|X}}}}
+
{{dsc|{{tt|T}}|the {{tt|value_type}} of {{tt|X}}}}
 +
{{dsc hitem|Value|Definition}}
 +
{{dsc|{{c|a}}|a value of type {{tt|X}}}}
 
{{dsc end}}
 
{{dsc end}}
  
 
====Types====
 
====Types====
 
{|class=wikitable
 
{|class=wikitable
−
!Expression||Return type||Conditions
+
!Name
 +
!Type
 +
!Requirements
 
|-
 
|-
−
|{{c|X::reverse_iterator}}||Iterator type whose value type is {{tt|T}}||{{c|reverse_iterator<iterator>}}
+
|{{c/core|typename X::reverse_iterator}}
−
|-
+
|{{c/core|std::reverse_iterator<X::iterator>}}
−
|{{c|X::const_reverse_iterator}}||Constant iterator type whose value type is {{tt|T}}||{{c|reverse_iterator<const_iterator>}}
+
|an iterator type whose [[cpp/iterator|value type]] is {{tt|T}}
 
|-
 
|-
 +
|{{c/core|typename X::const_reverse_iterator}}{{nbsp}}
 +
|{{c/core|std::reverse_iterator<X::const_iterator>}}{{nbsp}}
 +
|a constant iterator type whose [[cpp/iterator|value type]] is {{tt|T}}
 
|}
 
|}
  
−
====Member functions====
+
====Expressions====
 +
The types {{tt|reverse_iterator}} and {{tt|const_reverse_iterator}} in the following table denote {{c/core|typename X::reverse_iterator}} and {{c/core|typename X::const_reverse_iterator}} respectively.
 +
 
 
{|class=wikitable
 
{|class=wikitable
−
!Expression||Return type||Conditions||Complexity
+
!Expression
 +
!Type
 +
!Semantics
 +
!{{nbsp}}Complexity{{nbsp}}
 
|-
 
|-
−
|{{c|a.rbegin()}}||{{c|reverse_iterator}}; {{c|const_reverse_iterator}} for constant {{c|a}}||{{c|reverse_iterator(end())}}||Constant
+
|{{c|a.rbegin()}}
 +
|{{tt|reverse_iterator}}<br>{{tt|const_reverse_iterator}} for constant {{c|a}}
 +
|{{c|reverse_iterator(a.end())}}
 +
|Constant
 
|-
 
|-
−
|{{c|a.rend()}}||{{c|reverse_iterator}}; {{c|const_reverse_iterator}} for constant {{c|a}}||{{c|reverse_iterator(begin())}}||Constant
+
|{{c|a.rend()}}
 +
|{{tt|reverse_iterator}}<br>{{tt|const_reverse_iterator}} for constant {{c|a}}
 +
|{{c|reverse_iterator(a.begin())}}
 +
|Constant
 
|-
 
|-
−
|{{c|a.crbegin()}}||{{c|const_reverse_iterator}}||{{c|const_cast<X const&>(a).rbegin()}}||Constant
+
|{{c|a.crbegin()}}
 +
|{{tt|const_reverse_iterator}}
 +
|{{c|const_cast<const X&>(a).rbegin()}}
 +
|Constant
 
|-
 
|-
−
|{{c|a.crend()}}||{{c|const_reverse_iterator}}||{{c|const_cast<X const&>(a).rend()}}||Constant
+
|{{c|a.crend()}}
 +
|{{tt|const_reverse_iterator}}
 +
|{{c|const_cast<const X&>(a).rend()}}
 +
|Constant
 
|}
 
|}
  
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* {{lc|std::list}}
 
* {{lc|std::list}}
 
* {{lc|std::vector}}
 
* {{lc|std::vector}}
 +
* {{lc|std::inplace_vector}}
 
* {{lc|std::map}}
 
* {{lc|std::map}}
 
* {{lc|std::multimap}}
 
* {{lc|std::multimap}}
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{
 
{
 
     std::vector<int> v = {3, 1, 4, 1, 5, 9};
 
     std::vector<int> v = {3, 1, 4, 1, 5, 9};
−
 
+
   
 
     for (std::vector<int>::const_reverse_iterator i{v.crbegin()}; i != v.crend(); ++i)
 
     for (std::vector<int>::const_reverse_iterator i{v.crbegin()}; i != v.crend(); ++i)
 
         std::cout << *i << ' ';
 
         std::cout << *i << ' ';
Line 62: Line 88:
 
9 5 1 4 1 3
 
9 5 1 4 1 3
 
}}
 
}}
 +
 +
===Defect reports===
 +
{{dr list begin}}
 +
{{dr list item|wg=lwg|dr=2105|std=C++98|before={{c/core|typename X::const_reverse_iterator}} was<br>required to be an iterator type of value type {{c/core|const T}}|after=required to be a constant<br>iterator type of value type {{tt|T}}}}
 +
{{dr list end}}
  
 
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}
 
{{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Latest revision as of 03:22, 5 September 2024

 
C++
 
C++ named requirements
 

A ReversibleContainer is a Container that has iterators that meet the requirements of either LegacyBidirectionalIterator or LegacyRandomAccessIterator. Such iterators allow a ReversibleContainer to be iterated over in reverse.

Contents

[edit] Requirements

A type satisfies ReversibleContainer if it satisfies Container, its iterator type belongs to the bidirectional or random access iterator categories and, given the following types and values, the semantic and complexity requirements in the tables below are satisfied:

Type Definition
X an ReversibleContainer type
T the value_type of X
Value Definition
a a value of type X

[edit] Types

Name Type Requirements
typename X::reverse_iterator std::reverse_iterator<X::iterator> an iterator type whose value type is T
typename X::const_reverse_iterator  std::reverse_iterator<X::const_iterator>  a constant iterator type whose value type is T

[edit] Expressions

The types reverse_iterator and const_reverse_iterator in the following table denote typename X::reverse_iterator and typename X::const_reverse_iterator respectively.

Expression Type Semantics  Complexity 
a.rbegin() reverse_iterator
const_reverse_iterator for constant a 		reverse_iterator(a.end()) Constant
a.rend() reverse_iterator
const_reverse_iterator for constant a 		reverse_iterator(a.begin()) Constant
a.crbegin() const_reverse_iterator const_cast<const X&>(a).rbegin() Constant
a.crend() const_reverse_iterator const_cast<const X&>(a).rend() Constant

[edit] Standard library

[edit] Example

The following example iterates over a vector (which has random-access iterators) in reverse.

Run this code
#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v = {3, 1, 4, 1, 5, 9};
 
    for (std::vector<int>::const_reverse_iterator i{v.crbegin()}; i != v.crend(); ++i)
        std::cout << *i << ' ';
    std::cout << '\n';
}

Output: 

9 5 1 4 1 3

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2105 C++98 typename X::const_reverse_iterator was
required to be an iterator type of value type const T 		required to be a constant
iterator type of value type T
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