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Youwen Wu
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Co-authored-by: Ananth Venkatesh <dev.quantum9innovation@gmail.com>
70 lines
2.9 KiB
Markdown
70 lines
2.9 KiB
Markdown
# Suntheme
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Runs a script on sunrise and sunset, written in pure Haskell
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---
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You may be wondering how a program written in Haskell, the purely functional
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programming language, could possibly act on the real world by running a so-called "script."
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It's simple. We take in the entire World as an input to a pure function, the IO Monad.
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It then maps the original World to a new (generated) World, with our desired IO actions carefully applied with mathematical precision.
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> From the second perspective, an IO action transforms the whole world. IO actions are actually pure, because they receive a unique world as an argument and then return the changed world.
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See [this](https://lean-lang.org/functional_programming_in_lean/monads/io.html) for more information.
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Furthermore, you may wonder how this `suntheme` could possibly be used on a
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_purely functional_ Linux distribution, like NixOS. Wouldn't mutating the
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system colorscheme be pathologically changing the system state? This is simple
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as well. We simply utilize the NixOS specializations feature to generate _two
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copies_ of every single generation, one in dark and one in light theme, and
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then _swap out the entire system_. Therefore no state is mutated and the user
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simply gets swapped onto a specialized generation of NixOS with their desired
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colorscheme. Behold: the genius of purely functional programming.
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Work is ongoing to create a turnkey drop-in NixOS module that interfaces with
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Stylix to automatically create the system color activation scripts and expose
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them to `suntheme`.
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## Hacking on suntheme
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It's trivial to get started with suntheme development thanks to [Nix](https://nixos.org/), the purely functional package manager.
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Naturally, we leverage it as our primary package manager, both for Hackage and development tools like language servers and the like.
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First, install Nix through your preferred avenue or local system administrator. If unsure, we recommend [the Determinate Nix Installer](https://github.com/DeterminateSystems/nix-installer).
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Make sure flakes and nix-command are enabled (the Determinate Installer will enable them by default).
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Once you have `nix`, simply type:
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```bash
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nix develop
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```
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Say yes to any prompts asking you to allow substituters or trust public keys.
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Nix will fetch all of the required packages, such as GHC and Hackage dependencies.
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Additionally, you will have access to `hlint` and the `haskell-language-server`.
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To create a build, type
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```bash
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nix build
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```
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A binary will be produced in `result/bin/suntheme`.
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To make `suntheme` available in the shell without outputting to `result`, use
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```bash
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nix shell
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```
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This will build a binary just like `nix build` but add it temporarily to the PATH, so you can just type `suntheme`.
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To build and run `suntheme` immediately without adding it to the PATH, use
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```bash
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nix run
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```
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This will build a binary just like `nix shell` but immediately execute it.
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