https://github.com/ekzhang/ukanren-rs

Rust implementation of µKanren, a featherweight relational programming language.
https://github.com/ekzhang/ukanren-rs

functional-programming language logic-programming microkanren minikanren prolog rust

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Rust implementation of µKanren, a featherweight relational programming language.

• Host: GitHub
• URL: https://github.com/ekzhang/ukanren-rs
• Owner: ekzhang
• License: mit
• Created: 2021-09-10T03:28:18.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2023-01-01T20:59:49.000Z (about 2 years ago)
• Last Synced: 2024-05-22T22:32:27.335Z (8 months ago)
• Topics: functional-programming, language, logic-programming, microkanren, minikanren, prolog, rust
• Language: Rust
• Homepage: https://docs.rs/ukanren
• Size: 38.1 KB
• Stars: 107
• Watchers: 3
• Forks: 5
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

• awesome-rust-formalized-reasoning - µKanren-rs - implementation of µKanren. (Kanren / Libraries)

README

        
# µKanren-rs

[](https://github.com/ekzhang/ukanren-rs)

[](https://crates.io/crates/ukanren)

[](https://docs.rs/ukanren)

[](https://github.com/ekzhang/ukanren-rs/actions?query=branch%3Amain)

This is a Rust implementation of µKanren, a featherweight relational programming

language. See the original Scheme implementation

[here](http://webyrd.net/scheme-2013/papers/HemannMuKanren2013.pdf) for

reference.

## Features

- Structural unification of Scheme-like cons cells.

- Streams implemented with the `Iterator` trait.

- State representation using a persistent vector with triangular substitutions.

- Conjunction, disjunction, and `fresh` based on traits (macro-free API).

- Lazy goal evaluation using inverse-η delay.

- Integer, `bool`, `char`, `&str`, and unit type atoms.

- Explicit `ToValue` trait that converts vectors and arrays into cons-lists.

- Convenience macro `state!` to inspect and specify state.

## Usage

Here's a simple example, which defines and uses the `appendo` predicate.

```rust

use ukanren::*;

fn appendo(first: Value, second: Value, out: Value) -> BoxedGoal> {

    eq(&first, &())

        .and(eq(&second, &out))

        .or(fresh(move |a: Value, d: Value, res: Value| {

            eq(&(a.clone(), d.clone()), &first)

                .and(eq(&(a, res.clone()), &out))

                .and(appendo(d, second.clone(), res))

        }))

        .boxed()

}

let iter = run(|x, y| appendo(x, y, [1, 2, 3, 4, 5].to_value()));

assert_eq!(

    iter.collect::>(),

    vec![

        state![(), [1, 2, 3, 4, 5]],

        state![[1], [2, 3, 4, 5]],

        state![[1, 2], [3, 4, 5]],

        state![[1, 2, 3], [4, 5]],

        state![[1, 2, 3, 4], [5]],

        state![[1, 2, 3, 4, 5], ()],

    ],

);

```

More examples can be found in the `tests/` folder and the API documentation.






Made by Eric Zhang for

CS 252r. All code is

licensed under the MIT License.