"Is there anything older than jQuery?" Combinatorial Logic. "Surely Combinatorial Logic is too old to ever appear in a web page's code." You would think not. And yet... https://raganwald.com/JQuery-Combinators/

At the turn of the century, OG blogger Joel Spolsky posited the "Joel Test," twelve simple yes/no questions that defined a reasonable-by-the-standards-of-the-day local optimum for shipping software. Some seem ridiculously obvious today, but weren't standard […] [Original post on functional.cafe]

source: @RandomHourlyDuckBot

Two questions to ask about every abstraction, and to answer in every pull request introducing an abstraction: 1. What does this make: - possible? - practical? - easy? 2. At what expense?

A Brutal Look at Balanced Parentheses, Computing Machines, and Pushdown Automata https://raganwald.com/2019/02/14/i-love-programming-and-programmers.html

Forget algebraic types, the Type Lords use Gallifrean types.

An essay written in a now-dated style: "Alice and Bobbie and Sharleen and Dyck." https://raganwald.com/2018/11/14/dyck-joke.html

Graphical interfaces optimized for "time to first render" that bounce around as pieces subsequently load offers a great example of software trying to make *itself* look good at the expense of the user's productivity and cognitive burden.

There are two ways to write production #typescript. One is to use such advanced type features that if it compiles at all, you can be sure there are no obvious bugs. The other is to write such straightforward, extremely simple types that there are obviously no bugs. Only a third method works.

Source: @RandomHourlyDuckBot

Since 1951.

Source: @RandomHourlyDuckBot

It’s a long-lost cause, but to this day I believe that traits would have been a better fit for JS/TS than classes, because traits are explicitly about composing behaviour, and so is JS. https://www.cs.cmu.edu/~aldrich/courses/819/Scha03aTraits.pdf

Compare and contrast: “Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp.”—Philip Greenspun With... “Any sufficiently complicated JavaScript application from 2015 contains an ad hoc, informally […]

JS/TS *finally* has methods for chaining iterators (take, filter, reduce, &c.) I'm sure @rauschma already has written clear, digestible descriptions of how to use these great new methods to write clear, digestible and performant code. I really ought to get around to updating my decades-old […]

One of the finest things ever written abut the state of computing... And an excellent shaggy dog story: “The Emperor's Old Clothes,” Dr. Tony Hoare's 1980 Turing Award lecture. http://pascal.hansotten.com/uploads/hoare/The%20Emperor's%20Old%20Clothes.pdf

Random musing: Indirection and polymorphism are coupled. We make something indirect so that we can write code that works on more than one of them. And further, the scope of our indirection is governed by the degree of polymorphism our code supports. A lot of this is implicit, but sometimes we […]

Syntax highlighting is a waste of a channel: https://buttondown.com/hillelwayne/archive/syntax-highlighting-is-a-waste-of-an-information/

Someone has hacked a pipe operator (-ish) syntax for JavaScript. I have done some wild stuff like this as well, and I think it's great for exploring possibilities. https://github.com/irony/aspipes

Seymour Papert, co-creator pf the LOGO programming language and champion of computers in education: http://papert.org/

“Algebraic Types are not Scary, Actually” Interesting essay for its genre, I just wish we didn’t have to frame straightforward things as "Not actually scary.” The very existence of headlines like this reinforces the idea that these ideas *are* scary, and more people will read the headline than […]

Reddit has rediscovered "Truncatable Primes in JavaScript" from 2017! https://raganwald.com/2017/12/14/73939133.html Confession: The slug is by far the best part of the post.

A long time ago, in a ruby-encrusted galaxy far, far away... https://raganwald.com/assets/books/kestrels-quirky-birds-and-hopeless-egocentricity.pdf

A serendipitous post on 🍊🕸️ today, considering that I am writing a trampoline for type-level TypeScript: https://kmicinski.com/functional-programming/2025/08/01/loops/

My first type-level TypeScript Y Combinator good enough to criticize: https://gist.github.com/raganwald/6558ddfd76b16fe7b7213a80f54576e0

For the tenth time: https://en.wikipedia.org/wiki/Greenspun%27s_tenth_rule

A type-level TypeScript implementation of the Mockingbird. The Why Bird and Jackson’s Widowbird are next...

“[Structure and Interpretation of Computer Programs] wasn't really about Scheme; I think a lot of the point of using Scheme (as I understood it) is that the language is so minimalist and so beautiful that even this first intro course can be about fundamental […] [Original post on functional.cafe]

LLMs hallucinating a book I didn’t write is adjacent to a dangerous problem with LLMs generating code: LLMs have hallucinated libraries that don’t exist, and bad actors quickly created malware packages to match the hallucinating LLMs’ imports. Presto! Vibe […] [Original post on social.bau-ha.us]

Parsing With SNOBOL (2015) A programmer writes a blog post demystifying compilers including 600 lines of Java to parse finite state machines. Another programmer writes the same parser in 40 lines of F# using the Parser library. The first programmer claims it's even shorter in SNOBOL. The […]

A pattern for implementing Higher-Kinded Types in TypeScript: https://code.lol/post/programming/higher-kinded-types/ And the maturation of this concept into a full library: https://github.com/poteat/hkt-toolbelt#readme

“...We’re done. And this is a win over the typical recursive or even iterative solution for large numbers, because while each operation is more expensive, we only perform log2n operations.” —An ES6 function to compute the nth Fibonacci number (2015) […] [Original post on functional.cafe]

An online FRACTRAN “course” that teaches FRACTRAN programming patterns with a series of problems to solve using its built-in interpreter. https://trkern.itch.io/fractran

In 1972, John Horton Conway invented the FRACTRAN programming language to show that a generalization of the Collatz problem is algorithmically undecidable. He showed that this generalized form is equivalent to FRACTRAN programs, and also that FRACTRAN […] [Original post on functional.cafe]

The SNOBOL4 Programming Language, also known by its fans as, “The Green Book:” https://raganwald.com/assets/books/snobol-green-book.pdf

In 2004, Matthew Cook proved that the Rule 110 elementary cellular automaton is universal. His construction began with the existing proof that Post Tag Systems are universal, then introduced a variation, the Cyclic Tag System, which he showed is equivalent to […] [Original post on functional.cafe]

In 2004, Matthew Cook proved that the Rule 110 elementary cellular automaton is universal. His construction began with the existing proof that Post Tag Systems are universal, then introduced a variation, the Cyclic Tag System, which he showed is equivalent to […] [Original post on functional.cafe]

“DNA does not have one strand for animals, another for cats, and a third for jaguars. It does not compose these specializations together to produce the final specimen individual. DNA is a chaotic, unstructured mess. Einstein once said that “God does not play […] [Original post on functional.cafe]

“Prototypes in JavaScript are “just objects,” and since they are “just objects,” we can add, remove, or modify methods of the prototype by adding, removing, or modifying the functions bound to properties of the prototype.” —Prototypes are Objects (and why […] [Original post on functional.cafe]

“CoffeeScript Ristretto (2014) is a book about programming with functions that uses the CoffeeScript programming language for the examples and exercises. “CoffeeScript Ristretto's primary focus is functions as first-class values and advanced topics built on […] [Original post on functional.cafe]

“The command pattern was popularized by the 1994 book Design Patterns: Elements of Reusable Object-Oriented Software. But it’s 2016. Why do we care? Why is it worth another look?” —The annotated presentation of “First-Class Commands, an unexpectedly fertile […] [Original post on functional.cafe]

To Grok a Mockingbird (2018) “Using recursive combinators to enhance functional composition, with special guests the Mockingbird, Widowbird, and Why Bird” https://raganwald.com/2018/08/30/to-grok-a-mockingbird.html

Recursion? We don't need no stinking recursion! (2018): Seven different patterns for converting recursion to iteration in JavaScript. https://raganwald.com/2018/05/20/we-dont-need-no-stinking-recursion.html

Having our cake and eating it too: ”Using iterators to write highly composeable code“ (2017) https://raganwald.com/2017/04/19/incremental.html

Hashlife in the Browser, written for a presentation at SpainJS, 2013. Some glitches in 2025, but it computes the result of billions trillions, quadrillions, quintillions and higher orders of numbers of generations. The canvas has infinite scroll in every direction. https://raganwald.com/hashlife/