https://github.com/mystpi/act

🎬 Compose stateful actions to simulate mutable state
https://github.com/mystpi/act

functional-programming gleam monad state

Last synced: 17 days ago
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🎬 Compose stateful actions to simulate mutable state

• Host: GitHub
• URL: https://github.com/mystpi/act
• Owner: MystPi
• License: apache-2.0
• Created: 2024-03-24T18:54:31.000Z (almost 2 years ago)
• Default Branch: main
• Last Pushed: 2025-12-01T19:53:58.000Z (4 months ago)
• Last Synced: 2026-02-26T17:14:25.867Z (23 days ago)
• Topics: functional-programming, gleam, monad, state
• Language: Gleam
• Homepage: https://hexdocs.pm/act
• Size: 21.5 KB
• Stars: 27
• Watchers: 1
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE

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README

          
# 🎬 act

[![Package Version](https://img.shields.io/hexpm/v/act)](https://hex.pm/packages/act)

[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/act/)

Gleam is a functional programming language that does not support having _mutable state_. As such, programmers often have to pass state around manually, threading it through functions via arguments and return values. This can become a bit repetitive and clumsy.

What if state could be 'threaded' through functions automatically, with a nice API that resembles mutable state? This is the central idea of `act` and the [`Action`](https://hexdocs.pm/act/act.html#Action) type.

```gleam

type Action(result, state) = fn(state) -> #(state, result)

```

> `act` is inspired by the (now outdated) [gleam-eval](https://github.com/hayleigh-dot-dev/gleam-eval) package. `gleam-eval` is super cool, but only supports the `Result` type and was not created with Gleam's `use` feature in mind.

## Installation

```sh

gleam add act

```

## Docs & Example

Documentation can be found at . A simple example lives in [test/act_test.gleam](https://github.com/MystPi/act/blob/main/test/act_test.gleam).

## Development

```sh

gleam run   # Run the project

gleam test  # Run the tests

```