/*
* SPDX-License-Identifier: MIT
* Copyright (c) 2023 - 2026. The DeepCausality Authors and Contributors. All Rights Reserved.
*/
//! A commutative monoid: a [`Monoid`](crate::Monoid) whose `combine` is order-independent.
use crate::Monoid;
/// A **commutative monoid**: a [`Monoid`] whose operation additionally satisfies
///
/// - **Commutativity:** `x.combine(y) == y.combine(x)`.
///
/// This is the algebra a `Collection` folds through when child order carries no meaning — the
/// multiset / order-independence property (see `algebraic-causaloid-assumptions.md` #1) follows
/// from commutativity + associativity, not from an ad-hoc assumption.
pub trait CommutativeMonoid: Monoid {}