This article is a technical counterpart of my previous post Finding duplicated code with tools from your CS course. It is deliberately written in a terse manner, and I’m not going to hold your hand. Consider reading the previous post first and coming back here later.

Recently I was scrolling through brson’s Rust quote database and stumbled upon a link to the official Rust tutorial from the very beginning of 2013. It says Rust 0.6 in the corner, but it lists many things that were removed in 0.6, so it’s likely closer to 0.5. I heard tales of old Rust before, but not of how the...

Say you want to send a list of consumer records to another microservice over network via JSON. There are three concepts at play in this process: A logical value, which is how we humans treat the data. In this example, this would be “a list of consumer records”. This description does not specify how it’s represented...

Suppose that you’re writing a static analyzer and you want to write a diagnostic for match arms with equal bodies: match number { 1 => { // <-- let x = 1; f(x) } 2 => f(g(h())), 3 => "", 4 => { // <-- let x = 1; f(x) } _ => unreachable!(), }

Some time ago, I played around with decompiling Java class files in a more efficient manner than traditional solutions like Vineflower allow. Eventually, I wrote an article on my approach to decompiling control flow, which was a great performance boost for my prototype. At the time, I believed that this method can...

A few days ago, I stumbled upon a Hacker News discussion about the expression problem – a conundrum that occasionally arises in software design. Some of the commenters noted that Rust completely avoids this problem thanks to trait objects, and initially I agreed with them, but I’m now realizing it’s not at all as...

Fenwick trees and interval trees are well-known data structures in computer science. Interval trees in particular are commonly used in bioinformatics and computational geometry, and Fenwick trees are useful for keeping statistics. This post describes how the two can be merged to obtain a worst-case faster...

Here, read the intro of the Wikipedia page for Command pattern with me: In object-oriented programming, the command pattern is a behavioral design pattern in which an object is used to encapsulate all information needed to perform an action or trigger an event at a later time. You know what I call this? A function....

In contemporary “AI” discourse, people often make a point that LLM output cannot be trusted, since it contains hallucinations, often doesn’t handle edge cases properly, causes vulnerabilities, and so on. This is seen as an argument to never use LLM-generated code in production. Others argue that the benefits AI...

This is a tech phenomenon that I keep getting blindsided by no matter how much I try to anticipate it. Physical work feels difficult. You can look at someone and realize you don’t have nearly as much stamina, and even if you did, it still feels demanding. Research feels difficult. You’re tasked with thinking about...

I’m making progress on the Java decompiler I’ve mentioned in a previous post, and I want to share the next couple of tricks I’m using to speed it up. Java bytecode is a stack-based language, and so data flow is a bit cursed, especially when the control flow is complicated. I need to analyze data flow globally for...

This post is about a popular but niche technique I can never find a succinct reference for. I didn’t invent it, I just need a page I can link when giving optimization advice. Integer ↔ float casts that utilize specialized processor instructions, i.e. those that compilers use by default, typically have worse...