--- title: How to Choose Between Hindley-Milner and Bidirectional... description: The common question of whether to use Hindley-Milner (HM) or Bidirectional (Bidir) typing for a new programming language is a false dichotomy. The real... canonical: https://daily.dev/posts/how-to-choose-between-hindley-milner-and-bidirectional-typing-wdtkenmfn twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: How to Choose Between Hindley-Milner and Bidirectional Typing | daily.dev og:description: The common question of whether to use Hindley-Milner (HM) or Bidirectional (Bidir) typing for a new programming language is a false dichotomy. The real... og:url: https://daily.dev/posts/how-to-choose-between-hindley-milner-and-bidirectional-typing-wdtkenmfn og:image: https://api.daily.dev/og/posts/wDtKEnMFn.png og:image:alt: How to Choose Between Hindley-Milner and Bidirectional Typing 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. # How to Choose Between Hindley-Milner and Bidirectional Typing **[Hacker News](https://daily.dev/sources/hn)** · 6 min read · 0 upvotes · 0 comments ## Summary The common question of whether to use Hindley-Milner (HM) or Bidirectional (Bidir) typing for a new programming language is a false dichotomy. The real question is whether your language needs generics. Generics require unification, which is central to HM, but bidirectional typing is actually a superset of HM — it can incorporate unification just as well. Adding a `check` function alongside an HM `infer` function is all it takes to make a system bidirectional. The practical guidance: if you're building a general-purpose language, support generics and use unification within a bidirectional framework. If you're building a DSL or learning project where simplicity matters, annotation-driven bidirectional typing without unification is a valid, simpler choice. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Haskell for all: A bidirectional typechecking puzzle](https://daily.dev/posts/haskell-for-all-a-bidirectional-typechecking-puzzle-wbty7vdm3) · Planet Haskell · 0 upvotes · 0 comments - [A Guide to Typed Lambda Calculus](https://daily.dev/posts/a-guide-to-typed-lambda-calculus-qqejiz4hb) · Serokell · 0 upvotes · 0 comments - ["Five-Point Haskell": Total Depravity \(and Defensive Typing\)](https://daily.dev/posts/five-point-haskell-total-depravity-and-defensive-typing--xwwoyitrt) · Planet Haskell · 0 upvotes · 0 comments - [Haskell, Strong Types, and the Next Generation of Bioinformatics: interview with Michal Gajda](https://daily.dev/posts/haskell-strong-types-and-the-next-generation-of-bioinformatics-interview-with-michal-gajda-vqanncaau) · Serokell · 0 upvotes · 0 comments - [Learning Lean: Part 1](https://daily.dev/posts/learning-lean-part-1-ruwzozxws) · Hacker News · 0 upvotes · 0 comments --- Tags: [#type-systems](https://daily.dev/tags/type-systems) [View this post on daily.dev](https://daily.dev/posts/how-to-choose-between-hindley-milner-and-bidirectional-typing-wdtkenmfn) ```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":"How to Choose Between Hindley-Milner and Bidirectional Typing","url":"https://daily.dev/posts/how-to-choose-between-hindley-milner-and-bidirectional-typing-wdtkenmfn","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/how-to-choose-between-hindley-milner-and-bidirectional-typing-wdtkenmfn"},"datePublished":"2026-02-19T07:02:13.804Z","dateModified":"2026-02-19T07:02:35.699Z","description":"The common question of whether to use Hindley-Milner (HM) or Bidirectional (Bidir) typing for a new programming language is a false dichotomy. 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