What Comes to Mind

✌Existing Practice✌

2026-09-22 17:36

"Standardize existing practice" was barely true of the first C++ standard, and it is the wrong rule now. It was already being stretched in 1998. The ARM was existing practice. Templates as specified in the ARM were not what got standardized; the STL had two years of use at HP and a handful of early adopters before it was voted in; namespaces, exceptions as shipped, and iostreams with locales were designed in committee and implemented afterward. The result was a standard that no compiler implemented for years. We call it a success because C++ survived it, not because the process was sound.

Scrap Your static_assert

2026-08-10 18:12

The obvious way to test a compile-time fact is static_assert. It's right there, it needs no framework, and for a fact that has to hold it's the right tool. As a test, though, it has one bad property: a wrong answer is a translation failure. The build stops at the first one, you get a compiler diagnostic instead of a test result, and every other test in the file goes unrun. The xUnit report is empty. You learn that something is wrong, once, and nothing about the rest.

An Infix Backtick Operator for C++

2026-06-29 08:00

I am working on a proposal to let any callable be written between two backticks as an infix binary operator: x `f` y means exactly f(x, y). It is borrowed from Haskell, it desugars to an ordinary call, and I have it working in both Clang and GCC. This post is the announcement and the design tour.

Refreshing a Stale Git Subtree

2026-06-28 23:37

I write my WG21 papers with MPark/WG21, a Pandoc-based framework I vendor into the paper repo as a git subtree. The framework had a major overhaul–the build system split apart, and Pandoc jumped from 2.18 to 3.9–and my copy was 98 commits behind. Worse, the subtree had drifted in two directions at once: real local patches for a TLS-intercepting corporate network, and a pile of pointless autoformatter churn from my own pre-commit hooks. This is how I dragged it back to a verbatim copy of upstream, moved to the new flat.mk include, and pushed every local change back out of the subtree so the next update is a one-liner.

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.

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?