A few months ago, I set myself the challenge of writing a C compiler in 500 lines of Python1, after writing my SDF donut post. How hard could it be? The answer was, pretty hard, even when dropping quite a few features. But it was also pretty interesting, and the result is surprisingly functional and not too hard to understand! There's too much code for me to comprehensively cover in a single blog
Rewriting the Ruby parser
At Shopify, we have spent the last year writing a new Ruby parser, which we’ve called YARP (Yet Another Ruby Parser). As of the date of this post, YARP can parse a semantically equivalent syntax tree to Ruby 3.3 on every Ruby file in Shopify’s main codebase, GitHub’s main codebase, CRuby, and the 100 most popular gems downloaded from rubygems.org. We recently got approval to merge this work into C
Internet Engineering Task Force (IETF) K. Davis Request for Comments: 9562 Cisco Systems Obsoletes: 4122 B. Peabody Category: Standards Track Uncloud ISSN: 2070-1721 P. Leach University of Washington May 2024 Universally Unique IDentifiers (UUIDs) Abstract This specification defines UUIDs (Universally Unique IDentifiers) -- also known as GUIDs (Globally Unique IDentifiers) -- and a Uniform Resou
Golang Mini Reference 2022: A Quick Guide to the Modern Go Programming Language (REVIEW COPY)
Golang Mini Reference 2022 A Quick Guide to the Modern Go Programming Language (REVIEW COPY) Harry Yoon Version 0.9.0, 2022-08-24 REVIEW COPY This is review copy, not to be shared or distributed to others. Please forward any feedback or comments to the author. • feedback@codingbookspress.com The book is tentatively scheduled to be published on September 14th, 2022. We hope that when the release da
Parsing SQL - Strumenta
The code for this tutorial is on GitHub: parsing-sql SQL is a language to handle data in a relational database. If you worked with data you have probably worked with SQL. In this article we will talk about parsing SQL. It is in the same league of HTML: maybe you never learned it formally but you kind of know how to use it. That is great because if you know SQL, you know how to handle data. However
Most of my readers are probably familiar with procedural programming, object-oriented programming (OOP), and functional programming (FP). The majority of top programming languages on all of the language popularity charts (like TIOBE) support all three to some extent. Even if a programmer avoided one or more of those three paradigms like the plague, they’re likely at least aware of them and what th
Over the course of my Spring 2020 semester at Harvey Mudd College, I developed a self-hosting compiler entirely from scratch. This article walks through many interesting parts of the project. It’s laid out so you can just read from beginning to end, but if you’re more interested in a particular topic, feel free to jump there. Or, take a look at the project on GitHub. Table of contents What the pro
Patterns for Building LLM-based Systems & Products [ llm engineering production 🔥 ] · 66 min read Discussions on HackerNews, Twitter, and LinkedIn “There is a large class of problems that are easy to imagine and build demos for, but extremely hard to make products out of. For example, self-driving: It’s easy to demo a car self-driving around a block, but making it into a product takes a decade.”
Tier 4 Support § Support for these targets is entirely experimental. If this target is provided by LLVM, LLVM may have the target as an experimental target, which means that you need to use Zig-provided binaries for the target to be available, or build LLVM from source with special configure flags. zig targets will display the target if it is available. This target may be considered deprecated by
Zig in 30 minutes
test.md A half-hour to learn Zig This is inspired by https://fasterthanli.me/blog/2020/a-half-hour-to-learn-rust/ Basics the command zig run my_code.zig will compile and immediately run your Zig program. Each of these cells contains a zig program that you can try to run (some of them contain compile-time errors that you can comment out to play with) You'll want to declare a main() function to get
Solving Quantitative Reasoning Problems With Language Models
Solving Quantitative Reasoning Problems with Language Models Aitor Lewkowycz∗, Anders Andreassen†, David Dohan†, Ethan Dyer†, Henryk Michalewski†, Vinay Ramasesh†, Ambrose Slone, Cem Anil, Imanol Schlag, Theo Gutman-Solo, Yuhuai Wu, Behnam Neyshabur∗, Guy Gur-Ari∗, and Vedant Misra∗ Google Research Abstract Language models have achieved remarkable performance on a wide range of tasks that require
The Andrej Karpathy episode. Andrej explains why reinforcement learning is terrible (but everything else is much worse), why model collapse prevents LLMs from learning the way humans do, why AGI will just blend into the previous ~2.5 centuries of 2% GDP growth, why self driving took so long to crack, and what he sees as the future of education. Watch on YouTube; listen on Apple Podcasts or Spotify
This article was discussed on Hacker News. This is a continuation of my last post on how to write a tree-sitter grammar in an afternoon. Building on the grammar we wrote, now we’re going to write a linter for Imp, and it’s even easier! The final result clocks in less than 60 SLOC and can be found here. Recall that tree-sitter is an incremental parser generator. That is, you give it a description o
arXiv:2506.12115v1 [cs.CL] 13 Jun 2025 Eliciting Reasoning in Language Models with Cognitive Tools Brown Ebouky IBM Research - Zurich ETH Zurich Brown.Ebouky@ibm.com Andrea Bartezzaghi IBM Research - Zurich abt@zurich.ibm.com Mattia Rigotti IBM Research - Zurich mrg@zurich.ibm.com Abstract The recent advent of reasoning models like OpenAI’s o1 was met with excited spec- ulation by the AI community
Introduction Some part of me has always been fascinated with coercing code to run in weird places. I scratch this itch a lot with my security research projects. These often lead me to writing shellcode to run in kernels or embedded hardware, sometimes with the only way being through an existing bug. For those not familiar, shellcode is honestly hard to describe. I don’t know if there’s a very form
This past May, I started a new job working in Rust. I was somewhat skeptical of Rust for a while, but it turns out, it really is all it’s cracked up to be. As a long-time C++ programmer, and C++ instructor, I am convinced that Rust is better than C++ in all of C++’s application space, that for any new programming project where C++ would make sense as the programming language, Rust would make more
PEP 8 – Style Guide for Python Code Author: Guido van Rossum <guido at python.org>, Barry Warsaw <barry at python.org>, Alyssa Coghlan <ncoghlan at gmail.com> Status: Active Type: Process Created: 05-Jul-2001 Post-History: 05-Jul-2001, 01-Aug-2013 Table of Contents Introduction A Foolish Consistency is the Hobgoblin of Little Minds Code Lay-out Indentation Tabs or Spaces? Maximum Line Length Shoul
In this write-up, I will walk you through an implementation of a string formatting library for C++ I came up with for my video game. The end result came out really compact, at only 65 lines of code—providing a skeleton that can be supplemented with additional functionality at low cost. Usage Given a format buffer… char buffer[64]; String_Buffer buf = {str, sizeof str}; …the fmt::format function pr
A professional programmer delivers value through the authoring and maintaining of software that solves problems. (There are other important ways for professional programmers to deliver value but this post is about programming.) Programmers rely on various tools to author software. Arguably the most important and consequential choice of tool is the programming language. In this post, I will articul
Plan 9 Desktop Guide
PLAN 9 DESKTOP GUIDE INDEX What is Plan 9? Limitations and Workarounds Connecting to Other Systems VNC RDP SSH 9P Other methods Porting Applications Emulating other Operating Systems Virtualizing other Operating Systems Basics Window Management Copy Pasting Essential Programs Manipulating Text in the Terminal Acme - The Do It All Application Multiple Workspaces Tiling Windows Plumbing System Admin
Rust in Perspective
We are discussing and working toward adding the language Rust as a second implementation language in the Linux kernel. A year ago Jake Edge made an excellent summary of the discussions so far on Rust for the Linux kernel and we (or rather Miguel and Wedson) have made further progress since then. For the record I think this is overall a good idea and worth a try. I wanted to add some background tha
Over the past decade, my work has centred on partnering with teams to build ambitious products for the web across both desktop and mobile. This has provided a ring-side seat to a sweeping variety of teams, products, and technology stacks across more than 100 engagements. While I'd like to be spending most of this time working through improvements to web APIs, the majority of time spent with partne
Why APL is a language worth knowing
“A language that doesn't affect the way you think about programming, is not worth knowing.”, by Alan J. Perlis. Why APL is a language worth knowing Alan Perlis, the computer scientist recipient of the first Turing award, wrote “A language that doesn't affect the way you think about programming, is not worth knowing.” ― Alan J. Perlis, 1982. Special feature: Epigrams on programming. ACM Sigplan Not
Funny Programming Languages
January 19, 2023 Funny Programming Languages One of the weirdest and most wonderful things about people is that they can make a joke out of anything. For any human discipline there's people making jokes about that discipline. In programming, that starts with memes like "how do I exit vim" (as typified in places like r/programmerhumor), or funny examples of awful code (such as from TheDailyWTF).1 T
Exhaustive Union Matching in Python - Preferred Networks Research & Development
Pattern matching on algebraic data types is a powerful technique to process a given input and many programming languages have adopted it in one way or another. A check on whether a given match is “exhaustive”, i.e., covers all possible inputs, is helpful to avoid bugs when the set of possible inputs is extended; for example, when new enumeration values are added. In this blog post I will first bri
HTML Whitespace is Broken September 2, 2024Recently, I was working on a project which required a deeper understanding of how whitespace works in HTML. I was never a fan of HTML's whitespace behavior before as I've been burned by it a few times. But as I dug into it more deeply, I found myself discovering complex design issues that I wanted to explore in a blog post. This is partially to write down
Combobulate: Structured Movement and Editing with Tree-Sitter
Combobulate: Structured Movement and Editing with Tree-Sitter Combobulate is a package that adds advanced structured editing and movement to many programming modes in Emacs. Here's how it works, and how it can enrich your editing experience in Emacs. About a year ago I released an alpha – prototype, really – version of a tool I call Combobulate. I’d been using it personally for a while before I le
This page has two purposes: to describe how to implement computer language interpreters in general, and in particular to build an interpreter for most of the Scheme dialect of Lisp using Python 3 as the implementation language. I call my language and interpreter Lispy (lis.py). Years ago, I showed how to write a semi-practical Scheme interpreter Java and in in Common Lisp). This time around the go
Patching GCC to build Actually Portable Executables | Blog Needs a Name
Patching GCC to build Actually Portable Executables2023-07-13: I wrote a ~2000-line gcc patch to simplify building Actually Portable Executables with Cosmopolitan Libc. Now you can build popular software such as bash, curl, git, ninja, and even gcc itself, with Cosmopolitan Libc via the ./configure or cmake build system, without having to change source code, and the built executables should run on
Last month the V8 team published an excellent blog post on what they call the V8 Sandbox. This isn’t a sandbox for your JavaScript code — it’s intended to mitigate browser exploits caused by bugs in the JIT compiler itself. That’s important work because they report that most Chrome exploits start with a V8 memory safety bug. V8 is written in C++, so it may seem like these are the sort of bugs you’
Django for Startup Founders: A better software architecture for SaaS startups and consumer apps
In an ideal world, startups would be easy. We'd run our idea by some potential customers, build the product, and then immediately ride that sweet exponential growth curve off into early retirement. Of course it doesn't actually work like that. Not even a little. In real life, even startups that go on to become billion-dollar companies typically go through phases like: Having little or no growth fo
C++ safety, in context
Scope. To talk about C++’s current safety problems and solutions well, I need to include the context of the broad landscape of security and safety threats facing all software. I chair the ISO C++ standards committee and I work for Microsoft, but these are my personal opinions and I hope they will invite more dialog across programming language and security communities. Acknowledgments. Many thanks
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Writing a C compiler in 500 lines of Python
RFC 9562: Universally Unique IDentifiers (UUIDs)
Implementing Logic Programming
Kalyn: a self-hosting compiler for x86-64
Patterns for Building LLM-based Systems & Products
0.8.0 Release Notes ⚡ The Zig Programming Language
Andrej Karpathy — AGI is still a decade away
How to write a linter using tree-sitter in an hour
Eliciting Reasoning in Language Models with Cognitive Tools
Rust on MIPS64 Windows NT 4.0
Sayonara, C++, and hello to Rust!
PEP 8 – Style Guide for Python Code | peps.python.org
A string formatting library in 65 lines of C++
Gregory Szorc's Digital Home | Rust is for Professionals
If Not React, Then What? - Infrequently Noted
HTML Whitespace is Broken - Devel without a Cause
(How to Write a (Lisp) Interpreter (in Python))
Writing Truly Memory Safe JIT Compilers