uor-foundation 0.3.0

UOR Foundation — typed Rust traits for the complete ontology. Import and implement.
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// @generated by uor-crate from uor-ontology — do not edit manually

//! `recursion/` namespace — Self-referential computations with well-founded descent measures guaranteeing termination..
//!
//! Space: Kernel

use crate::HostTypes;

/// A self-referential computation parameterized by a descent measure. Each recursive step strictly decreases the measure; the computation terminates when the base case predicate is satisfied.
pub trait BoundedRecursion<H: HostTypes> {
    /// Associated type for `DescentMeasure`.
    type DescentMeasure: DescentMeasure<H>;
    /// The descent measure guaranteeing termination.
    fn measure(&self) -> &Self::DescentMeasure;
    /// Associated type for `BaseCase`.
    type BaseCase: BaseCase<H>;
    /// The base case match arm.
    fn base_case(&self) -> &Self::BaseCase;
    /// Associated type for `RecursiveCase`.
    type RecursiveCase: RecursiveCase<H>;
    /// The recursive case match arm.
    fn recursive_case(&self) -> &Self::RecursiveCase;
    /// Associated type for `Predicate`.
    type Predicate: crate::kernel::predicate::Predicate<H>;
    /// The predicate that identifies the base case.
    fn base_predicate(&self) -> &Self::Predicate;
    /// Associated type for `ComputationDatum`.
    type ComputationDatum: crate::user::morphism::ComputationDatum<H>;
    /// The computation applied at each recursive step (may reference itself via its content address).
    fn recursion_body(&self) -> &Self::ComputationDatum;
    /// The measure value at the start of recursion. Bounds the maximum recursion depth.
    fn initial_measure(&self) -> u64;
}

/// A well-founded function from computation state to xsd:nonNegativeInteger. Strictly decreases on every recursive step.
pub trait DescentMeasure<H: HostTypes> {
    /// The current value of the descent measure.
    fn measure_value(&self) -> u64;
}

/// The match arm selected when the descent measure reaches zero or the base predicate is satisfied. Produces a direct result without further recursion.
pub trait BaseCase<H: HostTypes>: crate::kernel::predicate::MatchArm<H> {}

/// The match arm selected when the descent measure is positive. Applies a decomposition step, decreases the measure, and invokes the recursion.
pub trait RecursiveCase<H: HostTypes>: crate::kernel::predicate::MatchArm<H> {}

/// A single step in a bounded recursion: the decomposition applied before the recursive invocation. Must strictly decrease the DescentMeasure.
pub trait RecursiveStep<H: HostTypes> {
    /// Associated type for `Transform`.
    type Transform: crate::user::morphism::Transform<H>;
    /// The transform applied to decompose the input before recursion.
    fn step_decomposition(&self) -> &Self::Transform;
    /// Associated type for `DescentMeasure`.
    type DescentMeasure: DescentMeasure<H>;
    /// The measure value before this step.
    fn step_measure_pre(&self) -> &Self::DescentMeasure;
    /// The measure value after this step.
    fn step_measure_post(&self) -> &Self::DescentMeasure;
}

/// A computation trace recording the sequence of recursive steps, measure values, and the base case result. The trace length is bounded by the initial measure value.
pub trait RecursionTrace<H: HostTypes>: crate::bridge::trace::ComputationTrace<H> {}

/// A bounded recursion where the descent measure is the structural size of the input type (site count, constraint count, or operad nesting depth).
pub trait StructuralRecursion<H: HostTypes>: BoundedRecursion<H> {}