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"Making Impossible States Impossible" by Richard Feldman

elm-conf · talk · Watch on YouTube

Functional programmingSoftware architecture & design

What it is

Richard Feldman's elm-conf talk on designing models so that bugs from impossible application states cannot occur, using Elm's compiler and types. It demonstrates techniques for making invalid states unrepresentable.

Why Hacker News recommends it

HN repeatedly recommends it as a talk that changed how people model data, with ideas that apply well beyond Elm to any typed language.

  • 9 people recommended it
  • 13 different months
  • 5 strong recommendations
  • first 2017, last 2026

What HN commenters said

  1. “Really changed how I think about programming.”

    Changed how they think about programming

    joshuahornby, 2018-01 · Strong recommendation · in “Ask HN: What’s your favorite talk from 2017?”

  2. “has given an absolute gem of a talk”

    Clear, concrete examples of making invalid states unrepresentable

    jasim, 2018-09 · Strong recommendation · in “Try OCaml”

  3. “has really changed the way I approach dealing with data in my code and was very insightful.”

    Changed how they model data in code

    kilian, 2018-10 · Strong recommendation · in “Ask HN: What are some of the best technical talks you've heard?”

  4. “the talks are geared towards elm but I think they offer some great advice applicable to programming in general.”

    Elm-focused talk with broadly applicable programming advice

    terminatornet, 2023-05 · Strong recommendation · in “Why I Use Elm in 2023”

  5. “There's a great talk on this subject by Richard Feldman from Elm Conf.”

    Talk on using types to make impossible states unrepresentable

    aczerepinski, 2017-09 · Recommendation · in “To type or not to type: quantifying detectable bugs in JavaScript”

  6. “I just watched a good Elm conference talk about this same concept”

    Good talk on the same concept as parse, don't validate

    bretthopper, 2019-11 · Recommendation · in “Parse, Don’t Validate”

  7. “A great talk on this subject is”

    Great talk on making invalid states unrepresentable

    1-more, 2020-10 · Recommendation · in “Applying “make invalid states unrepresentable””

  8. “It's a great way to keep you sane!”

    Technique for modeling state that keeps code sane

    jesperlang, 2020-10 · Recommendation · in “What can a pipe wrench teach us about software engineering?”

Excerpts from Hacker News comments, linked to the originals. Summaries and labels were written by a language model from those comments.

Topics: elm, type systems, make illegal states unrepresentable, functional programming, data modeling

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