#functional #functions #adt #kaguya


Functional Programming tools and ADTs

6 releases

Uses old Rust 2015

0.1.5 Jun 10, 2018
0.1.4 May 26, 2018

#1224 in Rust patterns


336 lines

License crates.io Build Status docs


  1. Introduction
  2. Install
  3. Usage
  4. Requirement
  5. Basic function
  6. Typeclass in rust as trait
  7. Typeclass impl for std struct and enum of Rust
  8. Contribution and developing
  9. Thanks List


KaguyaRs is a TOY functional library of Rust.

In fact, this is just the way I get familiar with Rust. I will try my best to implement as many as utilities. But NEVER try this in production environment UNTIL:

  1. Someday, I remove TOY in Introduction. OR
  2. I publish 1.0-stable version.

Key concerns of this library:

  1. May all the functions in this library are pure IF I CAN.
  2. Similar as 1, but pure -> lazy
  3. Base on 1, heavy clone may occur, persistance data structure will be introduced later to achive 4
  4. Performance. If not necessary trait object will be avoided.
  5. Implementation may be ugly and buggy, just feel free to issue it for any ideas.


Add dependency to your Cargo.toml

kaguya_rs = "*"


Please refer tests and Docs


  • toolchain: nightly
    • it can be normally used in stable, however feature is required for crate docs, clone repo if you want to use under stable
  • rustc version >= 1.26

Basic function

Basic function and its signature provided is listed below, function based on map will be applied later

There are two versions: function and macro

For curry version, it act as a macro. The macro will form a new closure, for example

let f = map(|x| x+1, [1,2,3,4,5]);
assert_eq!(f, [2,3,4,5,6]);

let f2 = map!(|x| x+1)([1,2,3,4,5]); // (Number -> Number) -> [Number] -> [Number]
assert_eq!(f2, [2,3,4,5,6])

For macro version, please refer test for further details as macro can curry automatically depends on the way to invoke macro.

For details, please refer TODO.md.

Typeclass in rust as trait

In Haskell, there are so many useful typeclass such as Monad, Functor, Applicative etc. I will implement as much as typeclass as I can. This can greatly empower ability of Functional Programming in Rust.

Typeclass impl for std struct and enum of Rust

There are some struct and enum that are widely used in Rust, e.g. Vec, HashMap, Option, Result etc. They can be treat as ADT that can impl typeclass of Haskell like Monad. I will implement them to enhance the power of std struct and enum.

Contribution and developing

Feel free to contribute and develop base on this lib. Make sure you MUST follow the constraint of LICENSE.

If you are interested to develop this library together, just make PRs OR send me a email to explain what you want to do for this library as a contributor.

For other questions, please create a new issue for following.

Thanks List


Apache License v2.

No runtime deps