effect-systems

This repository contains collections of code snippets related to my Effect Systems blog post. The post is not yet publically available.

As I’ve begun exploring the world of so-called algebraic effect systems, I’ve become increasingly frustrated in the level of documentation around them. Learning to use them (and moreso, understanding how they work) requires diving into the internals, watching various videos, and hoping to grok why certain effects aren’t being interpreted they way you might have hoped. My goal in this post is to address this issue, at least to some degree, in a focused, pedagogical fashion. In particular, I’ll aim to build up an intution of the fused-effects, library, chosen because it seems to have the most active development, the smallest dependency footprint, and minimal type machinery.

Building

This repository uses Nix for reproducible builds. First install Nix if you do not currently have it on your system. Afterward, enable flakes by adding line

experimental-features = nix-command flakes

to $HOME/.config/nix/nix.conf. You may then use nix build and nix develop. To makes things easier, we recommend using Home Manager to install direnv and nix-direnv. Once you run

$ direnv allow

from the root directory, nix develop will be automatically invoked each time a change is detected in flake.nix or you return to the directory.

Formatting

A pre-commit file is included in .githooks to ensure consistent formatting. Run the following to configure git to using it:

git config --local core.hooksPath .githooks/