--- title: Learn a language by writing too many Forths | daily.dev description: A practical approach to learning a new programming language: build increasingly complex Forth-like interpreters, starting from a simple RPN calculator,... canonical: https://daily.dev/posts/learn-a-language-by-writing-too-many-forths-d5t9klnmi twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Learn a language by writing too many Forths | daily.dev og:description: A practical approach to learning a new programming language: build increasingly complex Forth-like interpreters, starting from a simple RPN calculator,... og:url: https://daily.dev/posts/learn-a-language-by-writing-too-many-forths-d5t9klnmi og:image: https://api.daily.dev/og/posts/D5t9KLNMi.png og:image:alt: Learn a language by writing too many Forths 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. # Learn a language by writing too many Forths **[zserge's blog](https://daily.dev/sources/zserge)** · 13 min read · 0 upvotes · 0 comments ## Summary A practical approach to learning a new programming language: build increasingly complex Forth-like interpreters, starting from a simple RPN calculator, progressing to a tiny Forth with user-defined words, then implementing the esoteric FALSE language. The piece includes full Rust code for each stage and closes with a deep dive into virtual machine dispatch techniques (subroutine threading, direct threading with computed goto, indirect threading, switch/case dispatch, and continuation passing), comparing their performance characteristics in Rust. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What's a good project to build when learning a new programming language like Rust? Writing Forth-like interpreters works well because they touch fundamental concepts without requiring ecosystem research. Start with a simple RPN calculator to practice enums, loops, and error handling, then build a tiny Forth supporting word definitions with ':' and ';', and finally implement the esoteric FALSE language, whose original compiler was only 1024 bytes. _daily.dev surfaces language-learning project ideas like this for developers picking up a new stack._ ### What is the FALSE esoteric programming language and why is it interesting to implement? FALSE is an esoteric language created by Wouter van Oortmerssen in 1993, designed to be as powerful as possible with a minimal implementation; the original compiler fit in just 1024 bytes. It requires no parser since each character maps to a command, and it supports lambda functions, variables, arithmetic, conditionals, and loops, making it a compact but capable target for an interpreter exercise. _developers exploring compact language design can find writeups like this via daily.dev._ ### What's the difference between direct threading, indirect threading, and switch-based dispatch in a VM interpreter? Direct threading uses computed goto with command addresses as opcodes, jumping via a NEXT macro instead of returning from a call, and is faster than subroutine-call threading. Indirect threading, preferred by many Forth implementations, stores addresses of addresses for more compact code. Switch/case dispatch is more portable but incurs branching and bounds-checking overhead; in Rust benchmarks, subroutine calls were 2x-3x slower while switch/match dispatch matched continuation-passing performance. _daily.dev helps developers comparing VM dispatch techniques find deeper interpreter-design writeups._ ## Similar posts on daily.dev - [r3/doc/r3forth\_tutorial.md at main · phreda4/r3](https://daily.dev/posts/r3-doc-r3forth-tutorial-md-at-main-phreda4-r3-lyzrpv4rd) · Hacker News · 0 upvotes · 0 comments - [Teaching Kids Forth](https://daily.dev/posts/teaching-kids-forth-q4ty1fckn) · Hacker News · 4 upvotes · 2 comments --- Tags: [#rust](https://daily.dev/tags/rust) [View this post on daily.dev](https://daily.dev/posts/learn-a-language-by-writing-too-many-forths-d5t9klnmi) ```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":"Learn a language by writing too many Forths","url":"https://daily.dev/posts/learn-a-language-by-writing-too-many-forths-d5t9klnmi","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/learn-a-language-by-writing-too-many-forths-d5t9klnmi"},"datePublished":"2026-08-23T10:20:24.883Z","dateModified":"2026-08-23T10:21:56.289Z","description":"A practical approach to learning a new programming language: build increasingly complex Forth-like interpreters, starting from a simple RPN calculator,...","image":"https://media.daily.dev/image/upload/s--P4t4XyoV--/f_auto/v1722860399/public/Placeholder%2001","thumbnailUrl":"https://media.daily.dev/image/upload/s--P4t4XyoV--/f_auto/v1722860399/public/Placeholder%2001","isAccessibleForFree":true,"articleSection":"zserge's blog","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":"zserge's blog","logo":"https://media.daily.dev/image/upload/s--KQnFBOIT--/f_auto,q_auto/v1787480407/logos/zserge","url":"https://daily.dev/sources/zserge"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/learn-a-language-by-writing-too-many-forths-d5t9klnmi","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":0},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"rust","timeRequired":"PT13M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"zserge's blog","item":"https://daily.dev/sources/zserge"},{"@type":"ListItem","position":3,"name":"Learn a language by writing too many Forths"}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/learn-a-language-by-writing-too-many-forths-d5t9klnmi#faq","mainEntity":[{"@type":"Question","name":"What's a good project to build when learning a new programming language like Rust?","acceptedAnswer":{"@type":"Answer","text":"Writing Forth-like interpreters works well because they touch fundamental concepts without requiring ecosystem research. 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