13 Nov 2023
Macros are tricky beasts. Most languages—if they have macros at all—usually include a huge “here there be dragons” warning to warn curious would-be macro programmers of the dangers that lurk ahead.
What is it about macros that makes them so dangerous and unwieldy? That’s difficult to answer in general: there are many different macro systems with varying degrees of ease-of-use. Moreover, making macros easy to use safely is an open area of research—most languages that have macros don’t have features necessary to implement macros safely.
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14 Aug 2023
There’s a neat paper Type Systems as Macros by Chang, Knauth, and Greenman [1] that describes how to implement a typed language using an untyped host language and macro expansion. The paper is neat, but I found the code hard to follow—the paper uses a compact notation that’s convenient for print, but not so much for reproducing on one’s own. This post is my attempt to implement and explain in more accessible terms what’s presented in the paper.
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23 Jan 2023
Background # This is a question I’ve been wrestling with for a little bit. My first experience with a type system was with Java, and I didn’t like it. It just felt like an annoying constraint on the kinds of programs I could write. I was coming from Perl, which sports weak dynamic typing, so Java’s rigidity came as a bit of a shock.
After Java I learned some C, which too has types.
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17 Nov 2022
I had a friend ask me what continuations are, and why they're useful. There's a ton of literature about continuations; this is just a simple example meant to showcase something small and hopefully grokkable.
You will need to understand a little bit of Racket, but if you know any Scheme, that should be good enough. If you just want a quick primer, check out Learn X in Y minutes for Racket.
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27 Jul 2022
All the source for this may be found on my SourceHut repository.
Synopsis # Experimental type checker/inferer for a simple lambda calculus
Description # This is a type inference system for a little language. (Described below.) It uses a fusion of type inference algorithms from PLAI, ESP, and μKanren. (See Resources)
Broadly speaking, our type inference engine works by:
generating typing constraints from the program solving those constraints We’ll describe each of those in more detail.
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4 Jul 2022
μKanren (“micro-Kanren”) is a tiny, embeddable logic programming language. It’s easy to understand and implement in almost any language. It’s a great case study of an embedded language: unlike other common “embedded” languages like SQL or regex, which normally are represented as just plain-old strings, μKanren takes more advantage of the host language’s features.
I recommend reading the original paper: it’s short, well-written, and easy to understand.
I did a write-up which you can read on Sourcehut.
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7 Dec 2021
The following is from a essay from a class on German literature and film.
Fritz Lang’s movie Metropolis is primarily about the struggle between the oppressed working class and the ruling elite. What drives this tension, however, is a particular view of technology and technological progress that exacerbates the problems the film focuses on. This mentality is called high modernist ideology by Scott in his book Seeing Like a State:
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24 Oct 2021
Last week I was studying outside of a lecture hall where someone was teaching an introductory course on computer programming. There was a lot that I overheard that I disagreed with; this essay is an attempt to help me crystallize what exactly I disagreed with.
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