{"id":2876,"date":"2022-07-27T14:32:33","date_gmt":"2022-07-27T09:02:33","guid":{"rendered":"https:\/\/www.rangakrish.com\/?p=2876"},"modified":"2022-07-27T14:32:33","modified_gmt":"2022-07-27T09:02:33","slug":"understanding-stdspan","status":"publish","type":"post","link":"https:\/\/www.rangakrish.com\/index.php\/2022\/07\/27\/understanding-stdspan\/","title":{"rendered":"Understanding std::span"},"content":{"rendered":"

Introduced in C++20<\/strong><\/em>, std::span<\/strong><\/em><\/a>\u00a0is a light-weight abstraction that provides a convenient view<\/strong><\/em>\u00a0into a collection of contiguous<\/strong><\/em> elements. Note that it is not enough for the elements to be logically<\/strong><\/em> contiguous, but they must be contiguous in memory<\/strong><\/em> too. Thus, span<\/strong><\/em> will work with C-style arrays, C++ vectors and arrays. It will obviously not work with lists.<\/p>\n

The primary benefit of using span<\/strong><\/em> is that it provides a unified interface<\/strong><\/em> to work with the different types of collection.<\/p>\n

The following code is an example:<\/p>\n

\"Example-1:<\/a>
Example-1: span<\/strong><\/figcaption><\/figure>\n

The function printElements<\/strong><\/em> takes a span<int><\/strong><\/em> as argument and prints its elements. Even though this function is called in main<\/strong><\/em> with three different types of collections, span<\/strong><\/em> provides a common interface to access the respective elements.\u00a0<\/span><\/p>\n

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

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

The output is as expected.<\/p>\n

The reason span<\/strong><\/em> is light-weight is because it does not own<\/strong><\/em> the collection.<\/p>\n

It is also possible to work with dynamically allocated memory.<\/strong><\/em> The following example shows how we can use span<\/strong><\/em> along with unique_ptr<\/strong><\/em>. When constructing the span<\/strong><\/em> object, we additionally pass the element count.<\/p>\n

\"Using<\/a>
Using span with Dynamic Allocation<\/strong><\/figcaption><\/figure>\n

span<\/strong><\/em> provides a convenient indexing operator “[]”<\/strong> <\/em>to access individual elements of the collection it references. Note that we are able to modify<\/strong><\/em> the original collection through the span<\/strong><\/em>.<\/p>\n

Here is the program’s output.<\/p>\n

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

Another useful feature of span<\/strong><\/em> is being able to derive a “<\/strong>subspan”<\/strong><\/em> from a given span<\/strong><\/em>. Here is an example:<\/p>\n

\"Getting<\/a>
Getting a subspan<\/strong><\/figcaption><\/figure>\n

To further confirm that the subspan<\/strong><\/em> points to the second element (index: 1) of the original array, we compare the addresses. Look at the program’s output:<\/p>\n

\"Checking<\/a>
Checking subspan<\/strong><\/figcaption><\/figure>\n

The output shows that the values match, and even the addresses agree.\u00a0We can therefore conclude that the subspan<\/strong><\/em> is still a view into the original collection.<\/span><\/p>\n

Thus, span<\/strong><\/em> can be convenient when working with contiguously stored collections.<\/span><\/p>\n

That concludes our discussion of std::span<\/strong><\/em>.<\/p>\n

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

Introduced in C++20, std::span\u00a0is a light-weight abstraction that provides a convenient view\u00a0into a collection of contiguous elements. Note that it is not enough for the elements to be logically contiguous, but they must be contiguous in memory too. Thus, span will work with C-style arrays, C++ vectors and arrays. It will obviously not work with […]<\/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":[328,327],"class_list":["post-2876","post","type-post","status-publish","format-standard","hentry","category-c","category-programming","tag-c-collection","tag-stdspan"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9OLnF-Ko","jetpack-related-posts":[{"id":2024,"url":"https:\/\/www.rangakrish.com\/index.php\/2020\/06\/21\/stdis_standard_layout\/","url_meta":{"origin":2876,"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":717,"url":"https:\/\/www.rangakrish.com\/index.php\/2017\/12\/03\/c17-stdany\/","url_meta":{"origin":2876,"position":1},"title":"C++17: std::any","author":"admin","date":"December 3, 2017","format":false,"excerpt":"In the previous two posts, I talked about std::variant<> and std::optional<>. Today, I want to take up std::any for discussion. The type any (implemented by the class any) allows a variable to hold a single value of any type. More interestingly, the type of the value held by a variable\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Example1","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2017\/12\/Example1.png?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2017\/12\/Example1.png?resize=350%2C200 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2017\/12\/Example1.png?resize=525%2C300 1.5x"},"classes":[]},{"id":683,"url":"https:\/\/www.rangakrish.com\/index.php\/2017\/11\/05\/c17-stdvariant\/","url_meta":{"origin":2876,"position":2},"title":"C++17: std::variant","author":"admin","date":"November 5, 2017","format":false,"excerpt":"C++17 introduces a new type-safe union in the form of std::variant. At any time, it can store a single value from one of many types. We need to include \u00a0to use this feature. Let us look at a simple example to get started: First, we define a variant object v1\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Example1","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2017\/11\/Example1.png?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2017\/11\/Example1.png?resize=350%2C200 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2017\/11\/Example1.png?resize=525%2C300 1.5x"},"classes":[]},{"id":2889,"url":"https:\/\/www.rangakrish.com\/index.php\/2022\/08\/09\/stdarray-vs-stdvector\/","url_meta":{"origin":2876,"position":3},"title":"std::array vs. std::vector","author":"admin","date":"August 9, 2022","format":false,"excerpt":"One of the common questions when starting to study the container abstractions in C++20 is \"Should I use std::array\u00a0or std::vector?\". The correct answer is \"use what is best suited for the current situation\". That is not good enough, obviously. 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Almost all languages support this use case. Lisp, for example, has apply and funcall. When using apply, you can see that the arguments are passed via a separate list object. With funcall,\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"Calling Member Functions","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2018\/10\/Code5.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2018\/10\/Code5.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2018\/10\/Code5.png?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2018\/10\/Code5.png?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":2975,"url":"https:\/\/www.rangakrish.com\/index.php\/2022\/12\/25\/stdtie\/","url_meta":{"origin":2876,"position":5},"title":"Std::tie","author":"admin","date":"December 25, 2022","format":false,"excerpt":"std::tuple is a widely used abstraction in C++ and has been around since C++11. It is a generalization of std::pair. std::tie is convenient when we want to create a tuple of lvalue references to existing variables. It is a function template commonly used to unpack a tuple into individual objects.\u2026","rel":"","context":"In "C++"","block_context":{"text":"C++","link":"https:\/\/www.rangakrish.com\/index.php\/category\/c\/"},"img":{"alt_text":"std::tie Example","src":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2022\/12\/Example1-300x142.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2022\/12\/Example1-300x142.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.rangakrish.com\/wp-content\/uploads\/2022\/12\/Example1-300x142.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts\/2876","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=2876"}],"version-history":[{"count":0,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/posts\/2876\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/media?parent=2876"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/categories?post=2876"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rangakrish.com\/index.php\/wp-json\/wp\/v2\/tags?post=2876"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}