{"id":3153,"date":"2023-07-02T08:32:04","date_gmt":"2023-07-02T03:02:04","guid":{"rendered":"https:\/\/www.rangakrish.com\/?p=3153"},"modified":"2023-07-02T08:32:04","modified_gmt":"2023-07-02T03:02:04","slug":"the-sum-type-in-v-programming-language","status":"publish","type":"post","link":"https:\/\/www.rangakrish.com\/index.php\/2023\/07\/02\/the-sum-type-in-v-programming-language\/","title":{"rendered":"The Sum Type in V Programming Language"},"content":{"rendered":"

A S<\/strong>um<\/strong><\/em> data type in V language<\/strong><\/em><\/a> gives us a convenient way to hold objects of many distinct types (at any time, just one object) and hence is a discriminated union<\/strong><\/em>. For example, in C++<\/strong><\/em> we have the variant<\/strong><\/em><\/a> type.<\/p>\n

Here is an example of sum<\/strong><\/em> type in V<\/strong><\/em> language:<\/p>\n

\"The<\/a>
The “sum” Type<\/strong><\/figcaption><\/figure>\n

In the above program, the sum<\/strong><\/em> type Vehicle<\/strong><\/em> stands for the distinct types Car, Van <\/strong><\/em>and Bus<\/strong><\/em>.<\/p>\n

The corresponding output is:<\/p>\n

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

We can use the expression <var> is <Type><\/strong><\/em> to determine if a variable currently holds an object of type <Type><\/strong><\/em>:<\/p>\n

\"Using<\/a>
Using “is a” Expression<\/strong><\/figcaption><\/figure>\n

This prints:<\/p>\n

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

Likewise, we can use the expression <var> as <Type><\/strong><\/em> to dynamically cast the current object held in <var><\/strong><\/em> to the required <Type><\/strong><\/em>. As expected, this will trigger a panic if the casting is performed on an invalid type.<\/p>\n

This is shown below:<\/p>\n

\"Dynamic<\/a>
Dynamic Casting<\/strong><\/figcaption><\/figure>\n

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

\"Result<\/a>
Result of Dynamic Casting<\/strong><\/figcaption><\/figure>\n

It is often convenient to use the match<\/strong><\/em> expression to work with the individual variant in a sum<\/strong><\/em> type. This is cleaner than using multiple if statements. The print_vehicle<\/strong><\/em> function that we wrote earlier can be rewritten thus:<\/p>\n

\"Using<\/a>
Using “match” Expression<\/strong><\/figcaption><\/figure>\n

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

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

The match<\/strong><\/em> statement must specify a pattern for all variants of the type, or must include the else<\/strong><\/em> branch to handle what has been left out.<\/p>\n

Finally, the sum<\/strong><\/em> type is different from type inheritance as defined in object-oriented programming. In inheritance, when a class \u201cD\u201d<\/strong><\/em> is derived from a base class \u201cB\u201d<\/strong><\/em>, \u201cD\u201d<\/strong> is a<\/strong> \u201cB\u201d<\/strong><\/em>. In future, when another class \u201cE\u201d<\/strong><\/em> is derived from \u201cD\u201d<\/strong><\/em>, then that is also a \u201cB\u201d<\/strong><\/em>. In this sense, inheritance is a collection of one-way compatible open<\/strong><\/em> types. That is not the case with a sum<\/strong><\/em> type. It always defines a fixed and distinct set of types.<\/p>\n

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

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

A Sum data type in V language gives us a convenient way to hold objects of many distinct types (at any time, just one object) and hence is a discriminated union. For example, in C++ we have the variant type. Here is an example of sum type in V language: In the above program, the […]<\/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":[17,355],"tags":[364,356],"class_list":["post-3153","post","type-post","status-publish","format-standard","hentry","category-programming","category-vlang","tag-sum-type","tag-vlang"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9OLnF-OR","jetpack-related-posts":[{"id":3070,"url":"https:\/\/www.rangakrish.com\/index.php\/2023\/04\/02\/building-v-language-dll\/","url_meta":{"origin":3153,"position":0},"title":"Building V Language DLL","author":"admin","date":"April 2, 2023","format":false,"excerpt":"The relatively new V Programming Language (Vlang) boasts of some interesting features such as \u201cfast compilation\u201d and runtime performance \u201cas fast as C\u201d, at the same time being a \u201csimple language\u201d. 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