Simon Willison's Weblog: functional-programming

AoAH Day 15: Porting a complete HTML5 parser and browser test suite

2025-12-17T23:23:35+00:00

AoAH Day 15: Porting a complete HTML5 parser and browser test suite

Anil Madhavapeddy is running an Advent of Agentic Humps this year, building a new useful OCaml library every day for most of December.

Inspired by Emil Stenström's JustHTML and my own coding agent port of that to JavaScript he coined the term vibespiling for AI-powered porting and transpiling of code from one language to another and had a go at building an HTML5 parser in OCaml, resulting in html5rw which passes the same html5lib-tests suite that Emil and myself used for our projects.

Anil's thoughts on the copyright and ethical aspects of this are worth quoting in full:

The question of copyright and licensing is difficult. I definitely did some editing by hand, and a fair bit of prompting that resulted in targeted code edits, but the vast amount of architectural logic came from JustHTML. So I opted to make the LICENSE a joint one with Emil Stenström. I did not follow the transitive dependency through to the Rust one, which I probably should.

I'm also extremely uncertain about every releasing this library to the central opam repository, especially as there are excellent HTML5 parsers already available. I haven't checked if those pass the HTML5 test suite, because this is wandering into the agents vs humans territory that I ruled out in my groundrules. Whether or not this agentic code is better or not is a moot point if releasing it drives away the human maintainers who are the source of creativity in the code!

I decided to credit Emil in the same way for my own vibespiled project.

Via @avsm

Tags: definitions, functional-programming, ai, generative-ai, llms, ai-assisted-programming, ai-ethics, vibe-coding, ocaml, vibe-porting

Statically Typed Functional Programming with Python 3.12

2024-05-26T08:12:05+00:00

Statically Typed Functional Programming with Python 3.12

Oskar Wickström builds a simple expression evaluator that demonstrates some new patterns enabled by Python 3.12, incorporating the match operator, generic types and type aliases.

Via Lobste.rs

Tags: functional-programming, python

On Endings: Why & How We Retired Elm at Culture Amp

2023-04-10T02:11:46+00:00

On Endings: Why & How We Retired Elm at Culture Amp

Culture Amp made extensive use of Elm—a ML-like functional language that compiles to JavaScript—between 2016 and 2020 while building their company’s frontend. They eventually decided to move away from it, for reasons described at length in this post primarily relating to its integration with React. This piece is worth reading mainly as a thoughtful approach to engineering management challenge of deprecating a well-loved piece of technology from the recommended stack at a company.

Via lobste.rs

Tags: functional-programming, javascript, kevin-yank, management, react

Better Python Object Serialization

2020-01-07T20:35:22+00:00

Better Python Object Serialization

TIL about functions.singledispatch, a decorator which makes it easy to create Python functions with implementations that vary based on the type of their arguments and which can have additional implementations registered after the fact—great for things like custom JSON serialization.

Tags: functional-programming, json, python, serialization

Quoting Brian Goetz

2011-08-19T12:20:00+00:00

There is plenty of evidence in the ecosystem to support the hypothesis that, if given the tools to do so easily, object-oriented programmers are ready to embrace functional techniques (such as immutability) and work them into an object-oriented view of the world, and will write better, less error-prone code as a result. Simply put, we believe the best thing we can do for Java developers is to give them a gentle push towards a more functional style of programming.

— Brian Goetz

Tags: functional-programming, java, recovered

php: rfc: closures

2008-07-19T22:58:45+00:00

php: rfc: closures

I never thought I’d see the day, but a patch adding closures to PHP has been both proposed and accepted! Looks like a solid implementation—the syntax is similar to JavaScript but makes explicit which variables are to be captured. As with much of PHP, values are copied in to the closure by default but you can use an ampersand to specify JavaScript-style pass-by-reference instead.

Via Keeping Current With PHP

Tags: closures, functional-programming, javascript, php

In praise of functional programming

2003-04-29T23:57:55+00:00

Via Joe Gregorio, Functional programming in Python Part 1 and Part 2. I'm reading Structure and Interpretation of Computer Programs at the moment (available for free online, but I've got a library copy) and it has been getting me seriously interested in the functional programming paradigm. It's also by far the most enlightening (in terms of "wow, that really makes sense") computer science text book I've ever read. There's something naturally elegant about the functional style, probably thanks to the encapsulation encouraged by the lack of global variables and the extensive use of recursion in functional code examples. It's definitely true that exposure to a variety of programming styles encourages you to think about problems in different ways.

Tags: functional-programming, python