{"id":2128,"date":"2025-01-27T22:28:29","date_gmt":"2025-01-27T22:28:29","guid":{"rendered":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/?page_id=2128"},"modified":"2025-01-28T19:10:08","modified_gmt":"2025-01-28T19:10:08","slug":"member-templates","status":"publish","type":"page","link":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/topics\/c-details\/class-templates-2\/member-templates\/","title":{"rendered":"Member Templates"},"content":{"rendered":"\n

Member Templates<\/h2>\n\n\n\n

A function template or class template can be a member of an ordinary class, or of a class template.<\/p>\n\n\n\n

Here’s an example of an Outer<\/strong> template class that contains an Inner<\/strong> template class. It makes use of the std::complex<\/strong> class<\/a> from the C++ Standard Library.<\/p>\n\n\n\n

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\/\/<\/span><\/span>\n\/\/  InnerOuter.h<\/span><\/span>\n\/\/  Template Classes (Member Templates)<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/19\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#ifndef<\/span> InnerOuter_h<\/span><\/span>\n#define<\/span> InnerOuter_h<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><complex><\/span><\/span>\n<\/span>\ntemplate<\/span> <<\/span>class<\/span> <\/span>T<\/span>><\/span><\/span>\nclass<\/span> <\/span>Outer<\/span><\/span>\n{<\/span><\/span>\npublic:<\/span><\/span>\n  <\/span>Outer<\/span>( <\/span>std<\/span>::<\/span>complex<\/span><<\/span>double<\/span>> <\/span>c<\/span>, <\/span>double<\/span> <\/span>d<\/span>)<\/span><\/span>\n    : <\/span>m_inner<\/span>(c, d)<\/span><\/span>\n  {}<\/span><\/span>\n<\/span>\n  <\/span>template<\/span> <<\/span>class<\/span> <\/span>U<\/span>><\/span><\/span>\n  <\/span>U<\/span> <\/span>min<\/span>(<\/span>U<\/span> <\/span>v1<\/span>, <\/span>U<\/span> <\/span>v2<\/span>)<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>return<\/span> (v1 < v2) ? v1 : v2;<\/span><\/span>\n  }<\/span><\/span>\n  <\/span><\/span>\n  <\/span>std<\/span>::<\/span>complex<\/span><<\/span>double<\/span>> <\/span>getValue1<\/span>() <\/span>const<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>return<\/span> <\/span>m_inner<\/span>.<\/span>getValue1<\/span>();<\/span><\/span>\n  }<\/span><\/span>\n  <\/span><\/span>\n  <\/span>double<\/span> <\/span>getValue2<\/span>() <\/span>const<\/span><\/span>\n  {<\/span><\/span>\n    <\/span>return<\/span> <\/span>m_inner<\/span>.<\/span>getValue2<\/span>();<\/span><\/span>\n  }<\/span><\/span>\n<\/span>\nprivate:<\/span><\/span>\n  <\/span><\/span>\n  <\/span>template<\/span> <<\/span>class<\/span> <\/span>TYPE<\/span>><\/span><\/span>\n  <\/span>class<\/span> <\/span>Inner<\/span><\/span>\n  {<\/span><\/span>\n  <\/span>public:<\/span><\/span>\n    <\/span>Inner<\/span>(<\/span>TYPE<\/span> <\/span>v1<\/span>, <\/span>T<\/span> <\/span>v2<\/span>) <\/span><\/span>\n      : <\/span>m_value1<\/span>(v1), <\/span>m_value2<\/span>(v2) {}<\/span><\/span>\n    <\/span><\/span>\n    <\/span>TYPE<\/span> <\/span>getValue1<\/span>() <\/span>const<\/span> <\/span><\/span>\n    {<\/span><\/span>\n      <\/span>return<\/span> m_value1;<\/span><\/span>\n    }<\/span><\/span>\n    <\/span><\/span>\n    <\/span>T<\/span> <\/span>getValue2<\/span>() <\/span>const<\/span><\/span>\n    {<\/span><\/span>\n      <\/span>return<\/span> m_value2;<\/span><\/span>\n    }<\/span><\/span>\n    <\/span><\/span>\n  <\/span>private:<\/span><\/span>\n    TYPE m_value1;<\/span><\/span>\n    T    m_value2;<\/span><\/span>\n  };<\/span><\/span>\n<\/span>\n  Inner< <\/span>std<\/span>::complex<<\/span>double<\/span>> > m_inner;<\/span><\/span>\n    \/\/ NOTE THE AVOIDANCE OF >> !,<\/span><\/span>\n    \/\/ which was necessary in some earlier<\/span><\/span>\n    \/\/ versions of C++. Modern C++ compilers do<\/span><\/span>\n    \/\/ not have a problem with this.<\/span><\/span>\n};<\/span><\/span>\n<\/span>\n#endif<\/span> \/* InnerOuter_h *\/<\/span><\/span><\/code><\/pre><\/div>\n<\/div>\n\n\n\n
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… and a main program that exercises these template classes:<\/p>\n\n\n\n
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\/\/<\/span><\/span>\n\/\/  main.cpp<\/span><\/span>\n\/\/  Template Classes (Member Templates)<\/span><\/span>\n\/\/<\/span><\/span>\n\/\/  Created by Bryan Higgs on 10\/19\/24.<\/span><\/span>\n\/\/<\/span><\/span>\n<\/span>\n#include<\/span> <\/span><iostream><\/span><\/span>\n#include<\/span> <\/span><complex><\/span><\/span>\n#include<\/span> <\/span>"InnerOuter.h"<\/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  Outer<<\/span>double<\/span>> <\/span>o1<\/span>( <\/span>std<\/span>::<\/span>complex<\/span><<\/span>double<\/span>>(<\/span>23.4<\/span>, <\/span>11.7<\/span>), <\/span>56.8<\/span> );<\/span><\/span>\n  <\/span><\/span>\n  <\/span>int<\/span> i1 = <\/span>5<\/span>, i2 = <\/span>4<\/span>;<\/span><\/span>\n  <\/span>int<\/span> val = <\/span>o1<\/span>.<\/span>min<\/span>(i1, i2);<\/span><\/span>\n  <\/span><\/span>\n  <\/span>std<\/span>::cout << <\/span>"min("<\/span> << i1 << <\/span>","<\/span> << i2 << <\/span>") = "<\/span><\/span>\n            << val << <\/span>std<\/span>::endl;<\/span><\/span>\n<\/span>\n  <\/span>std<\/span>::cout << <\/span>"o1: value1 (complex<double>) : "<\/span><\/span>\n            << <\/span>o1<\/span>.<\/span>getValue1<\/span>() << <\/span>","<\/span> << <\/span>std<\/span>::endl<\/span><\/span>\n            << <\/span>" value2 (double) : "<\/span><\/span>\n            << <\/span>o1<\/span>.<\/span>getValue2<\/span>() << <\/span>std<\/span>::endl;<\/span><\/span>\n  <\/span><\/span>\n  <\/span>return<\/span> <\/span>0<\/span>;<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
It produces the following output:<\/p>\n\n\n\n
min(5,4) = 4\no1: value1 (complex<double>) : (23.4,11.7),\n value2 (double) : 56.8\nProgram ended with exit code: 0<\/strong><\/code><\/pre>\n<\/div>\n<\/div>\n\n\n\n
<\/div>\n\n\n\n
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Next: Summary of Class Templates<\/a><\/div>\n<\/div>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
Member Templates A function template or class template can be a member of an ordinary class, or of a class template. Here’s an example of an Outer template class that contains an Inner template class. It makes use of the std::complex class from the C++ Standard Library. … and a main program that exercises these […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2103,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-2128","page","type-page","status-publish","hentry"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2128","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=2128"}],"version-history":[{"count":3,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2128\/revisions"}],"predecessor-version":[{"id":2149,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2128\/revisions\/2149"}],"up":[{"embeddable":true,"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/pages\/2103"}],"wp:attachment":[{"href":"https:\/\/bhiggs.x10hosting.com\/PracticalCPlusPlusProgramming\/index.php\/wp-json\/wp\/v2\/media?parent=2128"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}