{"id":2190,"date":"2025-01-28T20:13:55","date_gmt":"2025-01-28T20:13:55","guid":{"rendered":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/?page_id=2190"},"modified":"2025-01-28T21:40:51","modified_gmt":"2025-01-28T21:40:51","slug":"adapters","status":"publish","type":"page","link":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/topics\/c-details\/the-standard-template-library-2\/adapters\/","title":{"rendered":"Adapters"},"content":{"rendered":"\n

<\/span>Adapters<\/span><\/h2>\n\n\n\n

An Adapter<\/strong><\/em> is a component that modifies the interface of another component.<\/p>\n\n\n\n

One example is a reverse_iterator<\/strong>, which adapts an iterator type into a type of iterator with all the capabilities of the original, but with the direction of traversal reversed.<\/p>\n\n\n\n

You can obtain a reverse_iterator<\/strong> by calling a container’s rbegin()<\/strong> or rend()<\/strong> methods.<\/p>\n\n\n\n

\n
\n
<\/path><\/path><\/svg><\/span>
\/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  STL Adapters<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/23\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><vector><\/span>      <\/span>\/\/ For vector<\/span><\/span>\n#include<\/span> <\/span><string><\/span>      <\/span>\/\/ For string<\/span><\/span>\n#include<\/span> <\/span><algorithm><\/span>   <\/span>\/\/ For for_each()<\/span><\/span>\n<\/span>\nvoid<\/span> <\/span>display<\/span>(<\/span>std<\/span>::<\/span>string<\/span> <\/span>x<\/span>)<\/span><\/span>\n{<\/span><\/span>\n  <\/span>std<\/span>::cout << x << <\/span>std<\/span>::endl;<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[]) <\/span><\/span>\n{<\/span><\/span>\n  <\/span>std<\/span>::string values[] =<\/span><\/span>\n    {<\/span>"Rose "<\/span>, <\/span>"Daffodil "<\/span>, <\/span>"Orchid "<\/span>, <\/span>"Tulip "<\/span>};<\/span><\/span>\n  <\/span>size_t<\/span> len = <\/span>sizeof<\/span>(values)\/<\/span>sizeof<\/span>(<\/span>values<\/span>[<\/span>0<\/span>]);<\/span><\/span>\n  <\/span><\/span>\n  \/\/ Initialize vector using pointer iterator<\/span><\/span>\n  <\/span>std<\/span>::vector<<\/span>std<\/span>::string> <\/span>v<\/span>(&<\/span>values<\/span>[<\/span>0<\/span>], &<\/span>values<\/span>[len]);<\/span><\/span>\n  <\/span><\/span>\n  \/\/ Use a regular iterator<\/span><\/span>\n  <\/span>for_each<\/span>(<\/span>v<\/span>.<\/span>begin<\/span>(), <\/span>v<\/span>.<\/span>end<\/span>(), display);<\/span><\/span>\n  <\/span>std<\/span>::cout << <\/span>std<\/span>::endl;<\/span><\/span>\n  <\/span><\/span>\n  \/\/ Use a reverse_iterator<\/span><\/span>\n  <\/span>for_each<\/span>(<\/span>v<\/span>.<\/span>rbegin<\/span>(), <\/span>v<\/span>.<\/span>rend<\/span>(), display);<\/span><\/span>\n  <\/span><\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
\n
… which outputs the following:<\/p>\n\n\n\n
Rose \nDaffodil \nOrchid \nTulip \n\nTulip \nOrchid \nDaffodil \nRose \nProgram ended with exit code: 0<\/strong><\/code><\/pre>\n<\/div>\n<\/div>\n\n\n\n
\n
The for_each Loop<\/strong><\/p>\n\n\n\n
Note the use of a for_each<\/strong> loop:<\/p>\n\n\n\n
for_each (InputIterator first, InputIterator last, Function fn)<\/strong>

first<\/strong> : The beginning position from where function operations are to be executed.
last<\/strong> : The ending position until where function has to be executed.
fn<\/strong> : The 3rd argument is a function or an object function specifying the operation to be applied to each element.<\/p>\n\n\n\n
for_each<\/strong> is defined in<\/p>\n\n\n\n
#include<algorithm><\/strong><\/em><\/p>\n<\/blockquote>\n\n\n\n
The calls to rbegin()<\/strong> and rend()<\/strong> return iterators of type vector<string>::reverse_iterator<\/strong>, which is defined as part of the vector<\/strong> interface.<\/p>\n\n\n\n
We could have used the following directly in the program:<\/p>\n\n\n\n
\n
\n
<\/path><\/path><\/svg><\/span>
reverse_iterator< <\/span>vector<\/span><<\/span>string<\/span>>::iterator > <\/span><\/span>\n      <\/span>start<\/span>( <\/span>v<\/span>.<\/span>end<\/span>() ), <\/span>finish<\/span>( <\/span>v<\/span>.<\/span>begin<\/span>() );<\/span><\/span>\nfor_each<\/span>(start, finish, display);<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
<\/div>\n<\/div>\n\n\n\n
<\/span>Container Adapters<\/span><\/h3>\n\n\n\n
With a Container Adapter<\/strong><\/em>, you can choose the interface you wish, and also the underlying structure.<\/p>\n\n\n\n
STL supplies three Container Adapters:<\/p>\n\n\n\n
    \n
  • stack<\/strong> : A Last-In, First-Out (LIFO) structure<\/li>\n\n\n\n
  • queue<\/strong> : Supports insertions at the back, and removals from the front.<\/li>\n\n\n\n
  • priority_queue<\/strong> : Supports insertions in sorted order, and removals from the front.<\/li>\n<\/ul>\n\n\n\n
    <\/span>The stack Container Adapter<\/span><\/h4>\n\n\n\n
    Here’s an example of the use of a stack<\/strong> container adapter:<\/p>\n\n\n\n
    \n
    \n
    <\/path><\/path><\/svg><\/span>
    \/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  STL Container Adapters<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/23\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><stack><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[])<\/span><\/span>\n{<\/span><\/span>\n  <\/span>std<\/span>::stack< <\/span>const<\/span> <\/span>char<\/span> * > s;  <\/span><\/span>\n      \/\/ Uses default deque implementation<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Nashua"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Manchester"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Hollis"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Milford"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Amherst"<\/span>);<\/span><\/span>\n  <\/span><\/span>\n  <\/span>while<\/span> (!<\/span>s<\/span>.<\/span>empty<\/span>())<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>s<\/span>.<\/span>top<\/span>() << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>s<\/span>.<\/span>pop<\/span>();<\/span>  \/\/ returns no value<\/span><\/span>\n  }<\/span><\/span>\n  <\/span><\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
    \n
    … which outputs:<\/p>\n\n\n\n
    Amherst\nMilford\nHollis\nManchester\nNashua\nProgram ended with exit code: 0<\/strong><\/code><\/pre>\n<\/div>\n<\/div>\n\n\n\n
    Or you can override the default implementation to use any of the sequence containers (vector<\/strong>, deque<\/strong>, or list<\/strong>):<\/p>\n\n\n\n
    \n
    \n
    <\/path><\/path><\/svg><\/span>
    \/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  STL Container Adapters<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/23\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><vector><\/span><\/span>\n#include<\/span> <\/span><stack><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[])<\/span><\/span>\n{<\/span><\/span>\n  \/\/std::stack< const char * > s;  <\/span><\/span>\n      \/\/ Uses default deque implementation<\/span><\/span>\n  <\/span>std<\/span>::stack< <\/span>const<\/span> <\/span>char<\/span> *, <\/span>std<\/span>::vector<<\/span>const<\/span> <\/span>char<\/span> *> > s; <\/span><\/span>\n      \/\/ uses vector<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Nashua"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Manchester"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Hollis"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Milford"<\/span>);<\/span><\/span>\n  <\/span>s<\/span>.<\/span>push<\/span>(<\/span>"Amherst"<\/span>);<\/span><\/span>\n  <\/span><\/span>\n  <\/span>while<\/span> (!<\/span>s<\/span>.<\/span>empty<\/span>())<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>s<\/span>.<\/span>top<\/span>() << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>s<\/span>.<\/span>pop<\/span>();<\/span>  \/\/ returns no value<\/span><\/span>\n  }<\/span><\/span>\n  <\/span><\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
    \n
    … which outputs:<\/p>\n\n\n\n
    Amherst\nMilford\nHollis\nManchester\nNashua\nProgram ended with exit code: 0<\/strong><\/code><\/pre>\n<\/div>\n<\/div>\n\n\n\n
    <\/span>The queue Container Adapter<\/span><\/h4>\n\n\n\n
    A queue<\/strong> container adapter may be implemented using either list<\/strong> or deque<\/strong> (the default).  <\/p>\n\n\n\n
    Here we use a list<\/strong>:<\/p>\n\n\n\n
    \n
    \n
    <\/path><\/path><\/svg><\/span>
    \/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  STL Container Adapters<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/23\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><list><\/span><\/span>\n#include<\/span> <\/span><queue><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[])<\/span><\/span>\n{<\/span><\/span>\n  <\/span>std<\/span>::queue< <\/span>const<\/span> <\/span>char<\/span> *, <\/span>std<\/span>::list<<\/span>const<\/span> <\/span>char<\/span> *> > q;  <\/span><\/span>\n      \/\/ Uses list<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Nashua"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Manchester"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Hollis"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Milford"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Amherst"<\/span>);<\/span><\/span>\n  <\/span><\/span>\n  <\/span>while<\/span> (!<\/span>q<\/span>.<\/span>empty<\/span>())<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>q<\/span>.<\/span>front<\/span>() << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>q<\/span>.<\/span>pop<\/span>();<\/span>  \/\/ returns no value<\/span><\/span>\n  }<\/span><\/span>\n  <\/span><\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
    \n
    … which outputs:<\/p>\n\n\n\n
    Nashua\nManchester\nHollis\nMilford\nAmherst\nProgram ended with exit code: 0<\/strong><\/code><\/pre>\n<\/div>\n<\/div>\n\n\n\n
    <\/span>The priority_queue Container Adapter<\/span><\/h4>\n\n\n\n
    A priority_queue<\/strong> container adapter may be implemented using a deque<\/strong> or a vector<\/strong> (the default is vector<\/strong>):<\/p>\n\n\n\n
    \n
    \n
    <\/path><\/path><\/svg><\/span>
    \/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  STL Container Adapters<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/23\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><vector><\/span><\/span>\n#include<\/span> <\/span><queue><\/span><\/span>\n#include<\/span> <\/span><string><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[])<\/span><\/span>\n{<\/span><\/span>\n  <\/span>std<\/span>::priority_queue< <\/span>std<\/span>::string > q;<\/span>  \/\/ Uses vector, less<T><\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Nashua"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Manchester"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Hollis"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Milford"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Amherst"<\/span>);<\/span><\/span>\n  <\/span>while<\/span> (!<\/span>q<\/span>.<\/span>empty<\/span>())<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>q<\/span>.<\/span>top<\/span>() << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>q<\/span>.<\/span>pop<\/span>();<\/span><\/span>\n  }<\/span><\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
    \n
    … which outputs:<\/p>\n\n\n\n
    Nashua\nMilford\nManchester\nHollis\nAmherst\nProgram ended with exit code: 0<\/strong><\/code><\/pre>\n<\/div>\n<\/div>\n\n\n\n
    Or we can change the priority ordering:<\/p>\n\n\n\n
    \n
    \n
    <\/path><\/path><\/svg><\/span>
    \/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  STL Container Adapters<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/23\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><vector><\/span><\/span>\n#include<\/span> <\/span><queue><\/span><\/span>\n#include<\/span> <\/span><string><\/span><\/span>\n<\/span>\nint<\/span> <\/span>main<\/span>(<\/span>int<\/span> <\/span>argc<\/span>, <\/span>const<\/span> <\/span>char<\/span> <\/span>*<\/span> <\/span>argv<\/span>[])<\/span><\/span>\n{<\/span><\/span>\n  \/\/std::priority_queue< std::string > q;  \/\/ Uses vector, less<T><\/span><\/span>\n  <\/span>std<\/span>::priority_queue<<\/span>std<\/span>::string,<\/span><\/span>\n                      <\/span>std<\/span>::vector<<\/span>std<\/span>::string>, <\/span><\/span>\n                      <\/span>std<\/span>::greater<<\/span>std<\/span>::string> > q;<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Nashua"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Manchester"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Hollis"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Milford"<\/span>);<\/span><\/span>\n  <\/span>q<\/span>.<\/span>push<\/span>(<\/span>"Amherst"<\/span>);<\/span><\/span>\n  <\/span>while<\/span> (!<\/span>q<\/span>.<\/span>empty<\/span>())<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>std<\/span>::cout << <\/span>q<\/span>.<\/span>top<\/span>() << <\/span>std<\/span>::endl;<\/span><\/span>\n    <\/span>q<\/span>.<\/span>pop<\/span>();<\/span><\/span>\n  }<\/span><\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
    \n
    … which outputs:<\/p>\n\n\n\n
    Amherst\nHollis\nManchester\nMilford\nNashua\nProgram ended with exit code: 0<\/strong><\/code><\/pre>\n<\/div>\n<\/div>\n\n\n\n
    <\/div>\n\n\n\n
    \n
    Next: Sorted Associative Containers<\/a><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
    Adapters An Adapter is a component that modifies the interface of another component. One example is a reverse_iterator, which adapts an iterator type into a type of iterator with all the capabilities of the original, but with the direction of traversal reversed. You can obtain a reverse_iterator by calling a container’s rbegin() or rend() methods. […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2150,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-2190","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2190","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/comments?post=2190"}],"version-history":[{"count":5,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2190\/revisions"}],"predecessor-version":[{"id":2226,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2190\/revisions\/2226"}],"up":[{"embeddable":true,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2150"}],"wp:attachment":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/media?parent=2190"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}