{"id":165455,"date":"2013-08-28T00:00:00","date_gmt":"2013-08-28T00:00:00","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/msr-research-item\/koka-programming-with-row-polymorphic-effect-types\/"},"modified":"2021-06-18T11:47:43","modified_gmt":"2021-06-18T18:47:43","slug":"koka-programming-with-row-polymorphic-effect-types","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/koka-programming-with-row-polymorphic-effect-types\/","title":{"rendered":"Koka: Programming with Row-Polymorphic Effect Types"},"content":{"rendered":"<div class=\"asset-content\">\n<p>Note: This is an updated article: a previous version of this article contained a wrong lemma and corresponding mistakes in various proofs of Section 5.<\/p>\n<p>We propose a programming model where effects are treated in a disciplined way, and where the potential side-effects of a function are apparent in its type signature. The type and effect of expressions can also be inferred automatically, and we describe a polymorphic type inference system based on Hindley-Milner style inference. A novel feature is that we support polymorphic effects through row-polymorphism using duplicate labels. Moreover, we show that our effects are not just syntactic labels but have a deep semantic connection to the program. For example, if an expression can be typed without an <i>exn<\/i> effect, then it will never throw an unhandled exception. Similar to Haskell&#8217;s `runST` we show how we can safely encapsulate stateful operations. Through the state effect, we can also safely combine state with let- polymorphism without needing either imperative type variables or a syntactic value restriction. Finally,our system is implemented fully in a new language called Koka and has been used successfully on various small to medium- sized sample programs ranging from a Markdown processor to a tier-splitted chat application.<\/p>\n<\/div>\n<p><!-- .asset-content --><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Note: This is an updated article: a previous version of this article contained a wrong lemma and corresponding mistakes in various proofs of Section 5. We propose a programming model where effects are treated in a disciplined way, and where the potential side-effects of a function are apparent in its type signature. The type and [&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":"Daan 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