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Ruby Conf 12 - Y Not- Adventures in Functional Programming by Jim Weirich

Confreaks · talk · Watch on YouTube

Functional programmingComputability & complexity theoryPython, Ruby & scripting languages

What it is

Jim Weirich's RubyConf 2012 talk derives the Y combinator step by step, live-coding in Ruby lambdas. It builds up an understanding of functional programming and lambda calculus from first principles.

Why Hacker News recommends it

HN recommends it repeatedly as one of the best and most entertaining programming talks, and as the talk that makes the Y combinator click, even for people who do not use Ruby.

  • 17 people recommended it
  • 18 different months
  • 9 strong recommendations
  • first 2013, last 2026

What HN commenters said

  1. “If you are curious about the topic, I strongly recommend watching these videos”

    Walks through the Y combinator and functional programming

    mekishizufu, 2013-11 · Strong recommendation · in “What is a y-combinator? (2008)”

  2. “This talk is a must-see, really shows off Jim Weirich's craft and overall ability to be a great pedagogue.”

    Showcases Jim Weirich's craft as a teacher

    VeejayRampay, 2014-02 · Strong recommendation · in “So very sad to hear about the passing of Ruby legend Jim Weirich”

  3. “perhaps the most entertaining and interesting technical talk I've ever seen.”

    Entertaining live-coded derivation that makes the topic approachable

    careersuicide, 2015-11 · Strong recommendation · in “Writing code doesn't mix well with oration”

  4. “Jim Wierich gave an incredible talk on the Y Combinator at RubyConf 2012.”

    Incredible talk and demonstration on the Y Combinator

    JamilD, 2016-12 · Strong recommendation · in “What is a Y Combinator?”

  5. “The first two talks that really blew my mind are”

    One of two talks that blew the commenter's mind

    webdevatlurk, 2018-04 · Strong recommendation · in “Ask HN: What is your favourite tech talk?”

  6. “Still one of the best programming talks I've ever seen.”

    Same lecture with slides alongside the talk

    dmvaldman, 2018-05 · Strong recommendation · in “Y Not? – Adventures in Functional Programming (2012)”

  7. “on lambda calculus and the (little 'c') Y combinator is fantastic.”

    Fantastic talk on lambda calculus and the Y combinator

    caseyohara, 2020-09 · Strong recommendation · in “All you need is λ, part one: booleans”

  8. “Great watch even though I never coded a line of Ruby.”

    Humorous one-hour explanation of the Y combinator, language-agnostic

    sva_, 2025-04 · Strong recommendation · in “Baking the Y Combinator from Scratch”

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

Topics: functional programming, lambda calculus, ruby, live coding, jim weirich

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