{"id":150254,"date":"2005-01-01T00:00:00","date_gmt":"2005-01-01T00:00:00","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/msr-research-item\/associated-types-with-class\/"},"modified":"2018-10-16T19:57:11","modified_gmt":"2018-10-17T02:57:11","slug":"associated-types-with-class","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/associated-types-with-class\/","title":{"rendered":"Associated types with class"},"content":{"rendered":"<div class=\"asset-content\">\n<p>In this paper, we explore an extension to Haskell type classes that allows a type class declaration to define data types as well as values (or methods). Similarly, an instance declaration gives a witness for such data types, as well as a witness for each method. It turns out that this extension directly supports the idea of a type-indexed type, and is useful in many applications, especially for self-optimising libraries that adapt their data representations and algorithms in a type-directed manner.<br \/>\nCrucially, just as Haskell&#8217;s existing type-class mechanism can be explained by translation into System F, so we can explain our extension by translation into System F, and we do so in full detail. This is a valuable property since it ensures that the addition of associated data types to an existing Haskell compiler leads to changes in the front end only. <a href=\"https:\/\/www.microsoft.com\/en-us\/research\/wp-content\/uploads\/2005\/01\/assoc.pdf\">assoc<\/a><\/p>\n<\/div>\n<p><!-- .asset-content --><\/p>\n<p>In this paper, we explore an extension to Haskell type classes that allows a type class declaration to define <em>data types<\/em> as well as <em>values<\/em> (or methods). Similarly, an instance declaration gives a witness for such data types, as well as a witness for each method. It turns out that this extension directly supports the idea of a type-indexed type, and is useful in many applications, especially for self-optimising libraries that adapt their data representations and algorithms in a type-directed manner.<\/p>\n<p>Crucially, just as Haskell&#8217;s existing type-class mechanism can be explained by translation into System F, so we can explain our extension by translation into System F, and we do so in full detail. This is a valuable property since it ensures that the addition of associated data types to an existing Haskell compiler leads to changes in the front end only.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In this paper, we explore an extension to Haskell type classes that allows a type class declaration to define data types as well as values (or methods). Similarly, an instance declaration gives a witness for such data types, as well as a witness for each method. It turns out that this extension directly supports the [&hellip;]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"_classifai_error":"","msr-author-ordering":[{"type":"user_nicename","value":"simonpj"}],"msr_publishername":"ACM Press","msr_publisher_other":"","msr_booktitle":"","msr_chapter":"","msr_edition":"POPL '05: Proceedings of the 32nd ACM SIGPLAN-SIGACT sysposium on Principles of programming languages","msr_editors":"","msr_how_published":"","msr_isbn":"1-58113-830-X","msr_issue":"","msr_journal":"","msr_number":"","msr_organization":"","msr_pages_string":"1\u201313","msr_page_range_start":"","msr_page_range_end":"","msr_series":"","msr_volume":"","msr_copyright":"","msr_conference_name":"POPL '05: Proceedings of the 32nd ACM SIGPLAN-SIGACT sysposium on Principles of programming 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