--- title: Bluefin | daily.dev description: Bluefin is a Haskell effect system that allows you to mix a variety of effects, such as early return, exceptions, I/O, mutable state, and streams. Effects are... canonical: https://daily.dev/posts/bluefin-rwvrch0oa twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Bluefin | daily.dev og:description: Bluefin is a Haskell effect system that allows you to mix a variety of effects, such as early return, exceptions, I/O, mutable state, and streams. Effects are... og:url: https://daily.dev/posts/bluefin-rwvrch0oa og:image: https://api.daily.dev/og/posts/Rwvrch0OA.png og:image:alt: Bluefin og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Bluefin **[Lobsters](https://daily.dev/sources/lobsters)** · 6 min read · 0 upvotes · 0 comments ## Summary Bluefin is a Haskell effect system that allows you to mix a variety of effects, such as early return, exceptions, I/O, mutable state, and streams. Effects are accessed through value-level handles, and Bluefin supports multiple effects of the same type. Exceptions in Bluefin are always handled and cannot escape the scope of their handler. Bluefin functions have a common type signature pattern, and the implementation style is similar to effectful. Tips for using Bluefin include using certain language extensions and writing explicit type signatures for handlers. Bluefin allows you to create your own effects, and an example is provided for counting positives and negatives using Bluefin. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: --- Tags: [#haskell](https://daily.dev/tags/haskell) [View this post on daily.dev](https://daily.dev/posts/bluefin-rwvrch0oa) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Bluefin","url":"https://daily.dev/posts/bluefin-rwvrch0oa","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/bluefin-rwvrch0oa"},"datePublished":"2024-04-26T01:26:16.206Z","dateModified":"2024-05-09T09:27:15.675Z","description":"Bluefin is a Haskell effect system that allows you to mix a variety of effects, such as early return, exceptions, I/O, mutable state, and streams. Effects are...","image":"https://media.daily.dev/image/upload/s--CxzD6vbw--/f_auto/v1722860399/public/Placeholder%2005","thumbnailUrl":"https://media.daily.dev/image/upload/s--CxzD6vbw--/f_auto/v1722860399/public/Placeholder%2005","isAccessibleForFree":true,"articleSection":"Lobsters","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Lobsters","logo":"https://media.daily.dev/image/upload/s--tl8v_Fku--/f_auto,t_logo/v1698841318/logos/lobste.jpg","url":"https://daily.dev/sources/lobsters"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/bluefin-rwvrch0oa","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"haskell","timeRequired":"PT6M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Lobsters","item":"https://daily.dev/sources/lobsters"},{"@type":"ListItem","position":3,"name":"Bluefin"}]} ```