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Eli Bendersky

Engineer at Google. Writes detailed technical posts on compilers, Go, Python, and computer science fundamentals.

https://eli.thegreenplace.net

Articles

How big are factorials?

The other day, I found myself wondering how big 52! (52 factorial) is, and that led me to ponder how these could be estimated without a calculator or a computer. It turns out there’s some fairly inter

Concurrent Servers: Part 8 - Go

This is part 8 in a series of posts on writing concurrent network servers. In this part, we'll switch to Go and see how it tackles the challenges described earlier in the series. All posts in the seri

Concurrent Servers: Part 7 - Rust

This is part 7 in a series of posts on writing concurrent network servers. In this part, we discuss how the challenges described in earlier parts are tackled in the Rust programming language. All post

Relative velocity and closing speed

In Physics simulations or game engines it’s sometimes useful to determine the speed with which two objects are approaching each other. This post will discuss the concept of closing speed, which is the

Notes on the Fourier Transform

The Fourier series is a great tool for analyzing periodic functions. But what about functions that don’t repeat? We’ve seen that we can compute Fourier series for a non-periodic function defined on a

Dot product: Component vs. Geometric definition

The goal of this post is to answer a simple question: why are the following two definitions of the vector dot product in Euclidean space [1] equivalent for vectors \vec{a} and \vec{b}: Component defin

Summary of reading: April - June 2026

"The Nuremberg Trial" by John Tusa and Ann Tusa - a detailed, meticulously researched account of the Nuremberg Trials. There's not a whole lot of side questing in this book - it's all focused on the t

Plugins case study: Pluggy

Recently I came upon Pluggy, a Python library for developing plugin systems. It was originally developed as part of the pytest project - known for its rich plugin ecosystem - and later extracted into

Thoughts on starting new projects with LLM agents

A few months ago I wrote about using LLM agents to help restructuring one of my Python projects. It's worth beginning by saying that the rewrite has been successful by all reasonable measures; I've be

Notes on Fourier series

The trigonometric Fourier series is a beautiful mathematical theory that shows how to decompose a periodic function into an infinite sum of sinusoids. These are my notes on the subject, with some exam

Scaling, stretching and shifting sinusoids

This is a brief and simple [1] explanation of how to adjust the standard sinusoid sin(x) to change its amplitude, frequency and phase shift. More precisely, given the general function: \[s(x)=A\cdot s

Thoughts on WebAssembly as a stack machine

This week the article Wasm is not quite a stack machine has been making the rounds and has caught my eye. The post claims that WASM is not a pure stack machine because it has locals and is missing som

Debugging WASM in Chrome DevTools

When I was working on the WASM backend for my Scheme compiler, I ran into several tricky situations with debugging generated WASM code. It turned out that Chrome has a very capable WASM debugger in it

watgo - a WebAssembly Toolkit for Go

I'm happy to announce the general availability of watgo - the WebAssembly Toolkit for Go. This project is similar to wabt (C++) or wasm-tools (Rust), but in pure, zero-dependency Go. watgo comes with

Summary of reading: January - March 2026

"Intellectuals and Society" by Thomas Sowell - a collection of essays in which Sowell criticizes "intellectuals", by which he mostly means left-leaning thinkers and opinions. Interesting, though certa

Notes on Lagrange Interpolating Polynomials

Polynomial interpolation is a method of finding a polynomial function that fits a given set of data perfectly. More concretely, suppose we have a set of n+1 distinct points [1]: \[(x_0,y_0), (x_1, y_1

Notes on Linear Algebra for Polynomials

We’ll be working with the set P_n(\mathbb{R}), real polynomials of degree \leq n. Such polynomials can be expressed using n+1 scalar coefficients a_i as follows: \[p(x)=a_0+a_1 x + a_2 x^2 + \cdots +

Rewriting pycparser with the help of an LLM

pycparser is my most widely used open source project (with ~20M daily downloads from PyPI [1]). It's a pure-Python parser for the C programming language, producing ASTs inspired by Python's own. Until

Compiling Scheme to WebAssembly

Author added a WebAssembly compiler to Bob, their 15-year-old Scheme implementation project, which already includes Python and C++ VMs.