Type Inference Was a Mistake
Type inference is bad. It makes code harder to read, and languages that use it too much are harder to write. It’s a false economy whereby you save unobservable milliseconds of typing today and make everything else worse. Type Inference Makes Code Less Readable If you have an IDE with a working LSP, you can hover over variables to see their types. In VSCode with rust-analyzer I can see the type ann
Two little interpreters
March 26, 2024 Late last year, I read a few blog posts that said something like “everyone knows that bytecode interpreters are faster than tree-walking interpreters”. And then I saw the paper AST vs. Bytecode: Interpreters in the Age of Meta-Compilation” when Stefan Marr shared a draft on Twitter. I realized that although I’d written a number of tree-walking interpreters, I’d never actually built
はじめてのインタープリター
インタープリターを書いたことがない方向けに、四則演算といった簡単なものから始め、少しずつ機能を足しながら言語を拡張していくような本です。
CS 6120: The Self-Guided Course
Syllabus Schedule Lessons Zulip Discussions Blog CS 6120: Advanced Compilers: The Self-Guided Online Course CS 6120 is a PhD-level Cornell CS course by Adrian Sampson on programming language implementation. It covers universal compilers topics like intermediate representations, data flow, and “classic” optimizations as well as more research-flavored topics such as parallelization, just-in-time com
Unification-free ("keyword") type checking
From my perspective, one of the biggest open problems in implementing programming languages is how to add a type system to the language without significantly complicating the implementation. For example, in my tutorial Fall-from-Grace implementation the type checker logic accounts for over half of the code. In the following lines of code report I’ve highlighted the modules responsible for type-che
Bergamot: Exploring Programming Language Inference Rules
Inference Rules and the Study of Programming Languages In this post, I will talk about inference rules, particularly in the field of programming language theory. The first question to get out of the way is “what on earth is an inference rule?”. The answer is simple: an inference rule is just a way of writing “if … then …”. When writing an inference rule, we write the “if” stuff above a line, and t
Firm - Optimization and Machine Code Generation
libFirm is a C library that provides a graph-based intermediate representation, optimizations, and assembly code generation suitable for use in compilers. Completely graph-based, source- and target-independent intermediate representation in SSA form Accompanying GCC-compatible C frontend with full C99 support Extensive set of optimizations High-quality register allocation Mature code generation su
Compiling Pattern Matching
Colin James obscurecolin [at] gmail (dot) com I am a computer programmer. I'm primarily interested in compilers for strict functional languages. Introduction This post intends to provide a brief overview of the algorithm described in Luc Maranget’s “Compiling Pattern Matching to Good Decision Trees”. I’m fond of this formalisation as it has a straightforward implementation and results in reasonabl
A Modern Compiler for the French Tax Code
In France, income tax is computed from taxpayers' individual returns, using an algorithm that is authored, designed and maintained by the French Public Finances Directorate (DGFiP). This algorithm relies on a legacy custom language and compiler originally designed in 1990, which unlike French wine, did not age well with time. Owing to the shortcomings of the input language and the technical limita
A response to 'A decade of developing a programming language'
I recently read the blog post A decade of developing a programming language by Yorick Peterse (found via Steve Klabnik). I thought it was an interesting blog post which got me thinking, and I have opinions on programming language design from Rust (it is almost exactly a decade since I got involved with Rust too), so I have written a response of sorts. This is all unsubstantiated opinion, so don't
A decade of developing a programming language
In 2013, I had an idea: "what if I were to build my programming language?". Back then my idea came down to "an interpreted language that mixes elements from Ruby and Smalltalk", and not much more. Between 2013 and 2015 I spent time on and off trying different languages (C, C++, D and various others I can't remember) to see which one I would use to build my language in. While this didn't help me fi
A new way to bring garbage collected programming languages efficiently to WebAssembly · V8
A recent article on WebAssembly Garbage Collection (WasmGC) explains at a high level how the Garbage Collection (GC) proposal aims to better support GC languages in Wasm, which is very important given their popularity. In this article, we will get into the technical details of how GC languages such as Java, Kotlin, Dart, Python, and C# can be ported to Wasm. There are in fact two main approaches:
Which Interpreters are Faster, AST or Bytecode?
This post is a brief overview of our new study of abstract-syntax-tree and bytecode interpreters on top of RPython and the GraalVM metacompilation systems, which we are presenting next week at OOPSLA. Prelude: Why Did I Build a Language on Top of the Truffle and RPython Metacompilation Systems? Writing this post, I realized that I have been working on interpreters on top of metacompilation systems
Ichigo Lispコンパイラ完全解説
Ichigo Lispコンパイラ完全解説 はじめに この記事では私がWebAssemblyで書いた Ichigo Lispという LISP 1.5実装のコンパイラのソースコードをすべて解説する。 というのも、最近とあるコンパイラの本を読んで 「説明が特定の実装に基づいてる割にそのソースが一部しか載ってない」 という不満を感じたのだが、自分で書いたコンパイラの記事 を読み返してみると、コンパイラのソースコードが一切出てこないことに気づいた。 こんな記事を書きながらよく人様の本に不満を持てたものだと 瀬戸内海より深く反省したので、 ここにIchigo Lispのコンパイラのすべてのソースコードを解説する。 想定読者とか Ichigo Lispのコンパイラは（ほとんど）すべてLISP 1.5で書かれている。 LISP 1.5特有のややこしい機能などは使っていないので、 Common Lisp、S
Implementing interactive languages
(This is part of a series on the design of a language. See the list of posts here.) Suppose I want to implement an interactive language - one where code is often run immediately after writing. Think scientific computing, database queries, system shells etc. So we care about both compile-time and run-time performance because we'll usually experience their sum. A traditional switch-based bytecode in
自作言語の紹介と関数型言語の実装方法の検討
はじめに 私が個人で昨年の 6 月ごろから開発している関数型プログラミング言語を紹介する。言語の名前は「Plato」である。 この言語は昨年の U22 プログラミングコンテスト最終発表会でも発表した。コンテスト後、コンパイラの構成と実装に関して調査し直して、コードを一から書き直した。コンパイラは Haskell で書かれているため、本稿の内容も Haskell の知識をベースとしている。また、型理論の知識もある程度求められる。ただ、大雑把に書いているため、大雑把に読めばよく、このブログの読解に正確さは必要無い。 このブログでは、まず Plato のチュートリアルを示し、実際に何ができるのかを説明する。次に型検査や中間言語の仕様などコンパイラの実装手法を大まかに説明する。最後に今後実現したい機能などについて述べる。理論的に面白いものや有用な機能については、後日それ専用の記事を書く予定。 チュ
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