{"id":2011,"date":"2020-06-06T16:06:21","date_gmt":"2020-06-06T10:36:21","guid":{"rendered":"https:\/\/www.rangakrish.com\/?p=2011"},"modified":"2020-06-06T18:34:44","modified_gmt":"2020-06-06T13:04:44","slug":"stdis_trivial","status":"publish","type":"post","link":"https:\/\/www.rangakrish.com\/index.php\/2020\/06\/06\/stdis_trivial\/","title":{"rendered":"std::is_trivial<>"},"content":{"rendered":"

Today let us try to understand the type trait std::is_trivial<T><\/strong><\/em>. This trait checks if the given type is a trivial<\/strong><\/em> type. For a precise definition of what trivial<\/strong><\/em> means, please visit the official page<\/strong><\/em><\/a>.<\/p>\n

As usual, we will go through three cases:<\/p>\n

– Primitive types<\/p>\n

– Classes without inheritance<\/p>\n

– Classes involving inheritance<\/p>\n

Case-1: Primitive Types<\/h3>\n

Take a look at the example below (as in the previous post, I am using the macro CHECK(T)<\/strong><\/em> to save some typing).\u00a0<\/span><\/p>\n

\"Primitive<\/a>
Primitive Types<\/strong><\/figcaption><\/figure>\n

The output is:<\/p>\n

\"Output<\/a>
Program Output<\/strong><\/figcaption><\/figure>\n

For convenience, the expected output is shown commented alongside the code. It is interesting that lvalue<\/strong><\/em> and rvalue references<\/strong><\/em> are not considered trivial, but pointer<\/strong><\/em> type is.<\/p>\n

Case-2: Classes without Inheritance<\/h3>\n

Let us look at the more interesting case involving classes. The image below shows different struct\/class\/union<\/strong><\/em> definitions.<\/p>\n

\"User-defined<\/a>
User-defined Types<\/strong><\/figcaption><\/figure>\n

Class “A”<\/strong><\/em> has some instance variables and a member function. However, it does not have a constructor or destructor.<\/p>\n

struct “B”<\/strong><\/em> does an inline initialization of a “const” field.<\/p>\n

struct “C”<\/strong><\/em> defines a constructor but no destructor.<\/p>\n

struct “D”<\/strong><\/em> defines a destructor but no constructor.<\/p>\n

struct “E”<\/strong><\/em> defines an instance variable of user-defined type “A”<\/strong><\/em>.<\/p>\n

“EArray”<\/strong><\/em> is a type that maps to an array of 10 elements of “E”<\/strong><\/em> type.<\/p>\n

struct “F”<\/strong><\/em> declares a deleted<\/strong><\/em> assignment operator.<\/p>\n

Finally, “U”<\/strong><\/em> is a union of three different types, one of which is a user-defined type “E”<\/strong><\/em>.<\/p>\n

Here is the code that checks these types:<\/p>\n

\"Example<\/a>
Example Program<\/strong><\/figcaption><\/figure>\n

What is the expected output? Here it is:<\/p>\n

\"Program<\/a>
Program Output<\/strong><\/figcaption><\/figure>\n

Case-3: Classes Involving Inheritance<\/h3>\n

Our final example uses a few classes as part of inheritance. Take a look:<\/p>\n

\"Inheritance<\/a>
Inheritance Example<\/strong><\/figcaption><\/figure>\n

Here is the output from the program:<\/p>\n

\"Program<\/a>
Program Output<\/strong><\/figcaption><\/figure>\n

The reason why “G”<\/strong><\/em> is not trivial is because it defines a virtual<\/strong><\/em> function. Since “H”<\/strong><\/em> derives from a trivial<\/strong><\/em> class “E”<\/strong><\/em> and adds nothing by itself, it is also a trivial<\/strong><\/em> type. Class “C”<\/strong><\/em> is not trivial<\/strong><\/em> and hence “I”<\/strong><\/em> is not trivial<\/strong><\/em> as well.<\/p>\n

The above use cases cover the essential properties of is_trivial<T><\/strong><\/em> trait. I hope you get the picture now.<\/p>\n

You can download the source code from here.<\/strong><\/em><\/a><\/p>\n

Have a nice weekend!<\/p>\n","protected":false},"excerpt":{"rendered":"

Today let us try to understand the type trait std::is_trivial<T>. This trait checks if the given type is a trivial type. For a precise definition of what trivial means, please visit the official page. As usual, we will go through three cases: – Primitive types – Classes without inheritance – Classes involving inheritance Case-1: Primitive […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[49,17],"tags":[67,240,235],"class_list":["post-2011","post","type-post","status-publish","format-standard","hentry","category-c","category-programming","tag-c","tag-is_trivial","tag-type-trait"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9OLnF-wr","jetpack-related-posts":[{"id":2024,"url":"https:\/\/www.rangakrish.com\/index.php\/2020\/06\/21\/stdis_standard_layout\/","url_meta":{"origin":2011,"position":0},"title":"std::is_standard_layout","author":"admin","date":"June 21, 2020","format":false,"excerpt":"In our last post, we learnt about the type trait std::is_trivial. Today, let us go through another type trait that is quite similar. The expression\u00a0is_standard_layout::value returns true if the layout of objects of type T is compiler independent, and hence is of standard format. Else, it returns false. This is\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"The Difference","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/06\/Example4.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/06\/Example4.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/06\/Example4.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/06\/Example4.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":1946,"url":"https:\/\/www.rangakrish.com\/index.php\/2020\/03\/28\/stdis_empty\/","url_meta":{"origin":2011,"position":1},"title":"std::is_empty","author":"admin","date":"March 28, 2020","format":false,"excerpt":"In the previous post, we looked at the std::is_destructible type trait. Today, let us try to understand another type trait std::is_empty. As per the specification, is_empty::value will return true in the following cases: - The class\/struct has no non-static data member - The class\/struct does not define a virtual function\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Example4: Union and Bit Field","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/03\/Example4-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/03\/Example4-1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/03\/Example4-1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":1960,"url":"https:\/\/www.rangakrish.com\/index.php\/2020\/04\/12\/stdcommon_type-type-trait\/","url_meta":{"origin":2011,"position":2},"title":"std::common_type Type Trait","author":"admin","date":"April 12, 2020","format":false,"excerpt":"In today's post, I would like to go over the type trait std::common_type<>. This trait was introduced in C++11. As per the specification, std::common_type::type refers to a type Tx in the given list, which the rest of the types in the list can be implicitly converted to. This\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Program Output","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/04\/Fig5.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":1973,"url":"https:\/\/www.rangakrish.com\/index.php\/2020\/04\/26\/stdis_base_of\/","url_meta":{"origin":2011,"position":3},"title":"std::is_base_of","author":"admin","date":"April 26, 2020","format":false,"excerpt":"In our on-going series on C++ Type Traits, today's topic is about the trait std::is_base_of<>. For the official description, see this. std::is_base_of::value takes two arguments, both classes (or structs), and returns true if A is a base class of B and false otherwise. Trivially, std::::value is true. Let\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Output","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/04\/Output.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":1928,"url":"https:\/\/www.rangakrish.com\/index.php\/2020\/03\/15\/stdis_destructible\/","url_meta":{"origin":2011,"position":4},"title":"std::is_destructible","author":"admin","date":"March 15, 2020","format":false,"excerpt":"In the last article, I explained the deleted destructor in some detail. Today, I would like to talk about a related construct, a type trait called std::is_destructible. Type traits, defined in the header , are a big help when it comes to implementing template metaprogramming. \u00a0See this\u00a0article for a nice\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Private\/Protected Destructor","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/03\/Example7.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/03\/Example7.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/03\/Example7.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":1992,"url":"https:\/\/www.rangakrish.com\/index.php\/2020\/05\/24\/stdis_convertible\/","url_meta":{"origin":2011,"position":5},"title":"std::is_convertible","author":"admin","date":"May 24, 2020","format":false,"excerpt":"The type trait is_convertible checks if an object of type From can be \"implicitly\" converted to an object of type To. The expression is_convertible::value returns true if implicit conversion is possible, else it returns false. For more details, please check out the reference. Let us look at three\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Support for Implicit Conversion","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/05\/Case3-1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/05\/Case3-1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2020\/05\/Case3-1.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts\/2011","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/comments?post=2011"}],"version-history":[{"count":0,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts\/2011\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/media?parent=2011"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/categories?post=2011"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/tags?post=2011"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}