#functional-programming #partial #functional #monoids #types #collection #learn

partial-functional

A small collection of Semigroups and Monoids for rust

1 unstable release

Uses new Rust 2021

0.1.0 Jun 26, 2022

#686 in Data structures

MIT license

33KB
832 lines

Partial Functional

This is a collection of some types from functional programming languages done in Rust. My main goal was to learn more rust and this came out of when I did a "partial-config" in Rust and decided to make it into a self contained crate.

Semigroup

A semigroup is a type that can be combined with another type to create a new one of the same type. The rust number primitives like u32 under the Addition operator is an example of that, e.g 5 + 2 will give a new u32 of 7. Some more interresting semigroups are Option if T is also a semigroup as well as Result<T, E> if both T and E are semigroups.

Monoid

A monoid is a subtrait of Semigroup with the additional property of identity. The empty identity and rusts standard library Default trait can be interchangibly used. Any type that implements Semigroup and Default will get a blanket implementation for Monoid.

Examples

Some other examples than listed below can be found under the examples directory in the source crate.

Here is a very trivial example from a Leetcode problem

use partial_functional::prelude::*;

fn max_profit(prices: Vec<u32>) -> u32 {
    let mut cheapest = Min::empty();
    let mut profit = Max::empty();

    for price in prices {
        cheapest = cheapest.combine(price.into());
        profit = profit.combine(Max(price - cheapest.0));
    }

    profit.0
}

Dependencies

~320–780KB
~18K SLoC