What Comes to Mind

Moving Forward With Legacy Encodings

2026-05-24 13:11

1. Abstract

Reverse-parsing legacy multibyte text encodings — such as Shift_JIS, Big5, or GB18030 — using only local context is an unsolvable problem. Unlike UTF-8, which guarantees \(O(1)\) self-synchronization, legacy encodings have heavily overlapping lead and trail byte ranges. Consequently, even if you begin at a known, valid character boundary, computing the byte-width of the preceding character requires an \(O(N)\) backward scan to the beginning of the string to resolve the parity of the sequence.

The WHATWG decoding algorithms provide no mitigation, as their forward-looking state machines reset completely at every boundary. Robust reverse iteration through these encodings cannot be solved algorithmically in situ; it requires maintaining an external cache of boundary offsets established during a forward pass.

What follows is the story of attempting to find a way out, and why the math forces us to fail.

Tailwind, Modus Themes, and the Blog Theming Workflow

2026-05-10 18:00

I replaced the Foundation 6 theme on this blog with Tailwind CSS. The immediate motivation was a CSS conflict—Foundation's global code and kbd rules bled into org-mode source blocks—but the deeper reason is that Tailwind has the community and documentation that Foundation no longer does.

This post documents the workflow: how the theme is structured, how syntax highlighting CSS connects Emacs to the browser, and what the current configuration choices are.

Surround With UUID

2026-04-09 17:41

The question of why C++ is standardized through ISO comes up fairly often. This is what I came up with as an explanation the last time I tried to answer that.

It's a radically oversimplified too long elevator pitch.

Why Standard Organizations

2026-03-07 10:21

The question of why C++ is standardized through ISO comes up fairly often. This is what I came up with as an explanation the last time I tried to answer that.

It's a radically oversimplified too long elevator pitch.

The Sender Sub-Language

2026-02-28 18:40

The paper The Sender Sub-Language by Vinnie Falco <vinnie.falco@gmail.com> and Mungo Gill <mungo.gill@me.com> makes extensive use of my work at https://github.com/steve-downey/sender-examples. The code is also the basis for my talk at C++Now 2023, Using the C++ Sender/Receiver Framework: Implement Control Flow for Async Processing. They present the code accurately and fairly, and I am very happy they found it useful in describing and understanding the capabilities of Senders in the framework. There is no higher praise than someone finding your work useful to build upon.

Nonetheless, we come to different overall conclusions about the Sender/Receiver framework.

Building vcpkg dependencies with project toolchain

2025-12-27 12:03

Making sure vcpkg delivers packages built with your toolchain is not hard, but much of the advice on the internet is flat wrong. You need to specify your toolchain both in your project and in the the vcpkg triplet. There's an airgap between your project and the dependency in vcpkg install. The CMake settings can't just flow through.

Substitution is Sometimes a Failure

2025-11-28 12:06

Why are optional::transform and optional::and_then not constrained by invocable?

Nikola Blog Infrastructure

2024-12-23 13:15

I've migrated from WordPress to a static blog generator–Nikola. This is how it works.

Concept Maps using C++23 Library Tech

2024-05-19 11:51

Abstract

C++0x Concepts had a feature Concept Maps that allowed a set of functions, types, and template definitions to be associated with a concept and the map to be specialized for types that meet the concept.

This allowed open extension of a concept.

Slides from C++Now 2023 Async Control Flow

2024-05-18 18:27

Using Sender/Receiver for Async Control Flow

Steve Downey

These are the slides, slightly rerendered, from my presentation at C++Now 2023.

Abstract

How can P2300 Senders be composed using sender adapters and sender factories to provide arbitrary program control flow?

How do I use these things?

Where can I steal from?