HackerTube.dev

What is PLUS times PLUS?

2swap · 2.2M views · 2025-03-23 · 28:28

Open on YouTube ↗

If playback is restricted in your region, try opening the original video. Use Mark watched to add it to your marked videos.

Overview

2swap explores lambda calculus using John Tromp's lambda diagrams, with animated beta-reductions, asking what PLUS times PLUS gives. It touches on Church encodings and the equivalence of Turing machines and lambda calculus.

On Hacker News

Mentioned in lambda calculus and combinator threads as a visual entry point to the topic.

Recommended by 1 HN people across 1 months · HN mentions 2025–2026

Topics

Computability & complexity theoryRecreational & visual mathFunctional programming
Search by tags
lambda diagramsbeta reductioncombinatorschurch encodingvisualization

What people said

contraposit · 2026-04 · Recommendation

I also liked the one on lambda calculus. I hope one day we will be able to find interpretation of what it actually means for PLUS Times Plus. Maybe this is how we will explore nonstandard arithmetic. What is PLUS times PLUS? [VIDEO]

Read the original HN comment ↗
observationist · 2026-03 · Reference

Combinators are math, and a little like Lisp - building functions from primitives and operations with the ability to apply them, where even the notion of variables are functions - functions all the way down. The y combinator is this: λf.(λx.x x)(λx.f(x x)) Lambda diagrams get you visualizations like this: [LINK] When considering logic and functions, when thinking in the space of combinators, you can ask questions like "What is Plus times Plus" and have a sensible result. [VIDEO] Combinators are awesome. The site linked by OP is a specific collection of combinators with bird names, riffing on the "To Mock a Mockingbird" puzzle book and subsequent meme of giving combinators bird names.

Read the original HN comment ↗
bntr · 2026-02 · Reference

For comparison: factorial(3) visualized in two different notations. John Tromp's Lambda Diagrams (via 2swap): [VIDEO] Bubble Notation: [LINK]

Read the original HN comment ↗

Sources

Video by 2swap, played through YouTube.

Data and selection notes

HN summaries and labels may contain AI errors. HN dates refer to discussions, not video publication.

HN Library: HackerTube export (2026-10-31) and open-index/hacker-news. Upstream summaries and classifications may contain AI errors.

Views, duration and playback status refresh separately from the published catalog. When an update fails, existing data remains visible.

Selection checks
  • SaaS & AI candidates: Topic keywords do not match
  • Editor-approved picks: Editorial review is required

Rule matches identify candidates. They do not guarantee video quality or financial results.

About the library and its sources