Exact geometry, written in Rust, by definition.

/// A vertex: a point stored by definition.
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub struct Vertex {
    /// The point.
    pub point: PointId,
}

/// An edge on a curve. Both ends `None` is a ring edge over a whole closed curve.
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub struct Edge {
    /// The curve.
    pub curve: CurveId,
    /// Edge direction relative to the curve's natural direction.
    pub sense: Sense,
    /// Start vertex along the edge direction.
    pub start: Option<VertexId>,
    /// End vertex along the edge direction.
    pub end: Option<VertexId>,
}

/// The result of one decision. See `docs/ARCHITECTURE.md`.
#[must_use]
#[derive(Clone, Debug, PartialEq)]
pub enum Outcome<T> {
    /// The strict answer is certified; the quantity is proven non-zero.
    Proven(T),
    /// The quantity is proven exactly zero.
    ProvenCoincident(Coincidence),
    /// The budget ran out; the quantity is proven to lie within the bound.
    NotExact(NotExact),
    /// The decision cannot be answered.
    Refused(Refusal),
}

let graph = run!(Stage::Intersect, intersect(model, a, b, dec));
let imprinted = run!(Stage::Imprint, imprint(model, &graph, dec));
let classes = run!(Stage::Classify, classify(model, &imprinted, dec));
let before = dec.stats().clone();
let selection = keep(&classes, &imprinted, op);
report.stages.push(StageRecord {
    stage: Stage::Keep,
    stats: statistics_delta(&before, dec.stats()),
    marks: 0,
});
let body = run!(Stage::Sew, sew(model, &imprinted, &selection, dec));