diff options
Diffstat (limited to 'chain/src/item')
| -rw-r--r-- | chain/src/item/default.rs | 547 | ||||
| -rw-r--r-- | chain/src/item/genins.rs | 231 | ||||
| -rw-r--r-- | chain/src/item/mod.rs | 252 |
3 files changed, 1030 insertions, 0 deletions
diff --git a/chain/src/item/default.rs b/chain/src/item/default.rs new file mode 100644 index 0000000..b71f940 --- /dev/null +++ b/chain/src/item/default.rs @@ -0,0 +1,547 @@ +//! This module provides a default implementation of iten derivation +//! forest. + +use super::*; +use graph::{ + builder::BuilderMut, labelled::binary::PLGBuilderMut, Graph, LabelGraph, PLGraph, RedirectGraph, +}; + +use core::fmt::Display; + +/// The type of errors for forest operations. +#[derive(Debug, Copy, Clone, PartialEq, Eq, Ord, PartialOrd)] +pub enum Error { + /// An index is out of bounds. + /// + /// The first component is the index that is out of bounds, and + /// the second component is the current length of nodes. + IndexOutOfBounds(usize, usize), + /// The forest does not permit duplicate nodes but encounters a + /// repeated node. + DuplicatedNode(usize), + /// A node has no labels while it is required to have one. + NodeNoLabel(usize), + /// Encounter an invalid error in converting from an error of + /// graphs. + InvalidGraphError(GError), + /// Encounter an error when converting forest labels. + LabelConversion(ForestLabelError), +} + +impl Display for Error { + fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + match self { + Error::IndexOutOfBounds(index, bound) => { + write!(f, "index {index} is out of bound {bound}") + } + Error::DuplicatedNode(n) => write!(f, "node {n} is duplicated"), + Error::InvalidGraphError(ge) => write!(f, "invalid error: {ge}"), + Error::NodeNoLabel(n) => write!(f, "node {n} has no labels, but it should have one"), + Error::LabelConversion(le) => write!(f, "fail to convert labels: {le}"), + } + } +} + +impl std::error::Error for Error {} + +impl From<GError> for Error { + fn from(ge: GError) -> Self { + match ge { + GError::IndexOutOfBounds(index, bound) => Self::IndexOutOfBounds(index, bound), + GError::DuplicatedNode(n) => Self::DuplicatedNode(n), + _ => Self::InvalidGraphError(ge), + } + } +} + +impl From<ForestLabelError> for Error { + fn from(le: ForestLabelError) -> Self { + Self::LabelConversion(le) + } +} + +/// A default implementation of forest. +#[derive(Debug, Clone)] +pub struct DefaultForest<T: GraphLabel> { + graph: PLGraph<T>, + root: Option<usize>, +} + +impl<T: GraphLabel> Default for DefaultForest<T> { + fn default() -> Self { + let graph = Default::default(); + let root = None; + + Self { graph, root } + } +} + +impl<T: GraphLabel> AsRef<DefaultForest<T>> for DefaultForest<T> { + fn as_ref(&self) -> &DefaultForest<T> { + self + } +} + +impl<T: GraphLabel> Graph for DefaultForest<T> { + type Iter<'a> = <PLGraph<T> as Graph>::Iter<'a> + where + Self: 'a; + + #[inline] + fn is_empty(&self) -> bool { + self.graph.is_empty() + } + + #[inline] + fn nodes_len(&self) -> usize { + self.graph.nodes_len() + } + + #[inline] + fn edges_len(&self) -> Option<usize> { + self.graph.edges_len() + } + + #[inline] + fn children_of(&self, node_id: usize) -> Result<Self::Iter<'_>, GError> { + self.graph.children_of(node_id) + } + + #[inline] + fn degree(&self, node_id: usize) -> Result<usize, GError> { + self.graph.degree(node_id) + } + + #[inline] + fn is_empty_node(&self, node_id: usize) -> Result<bool, GError> { + self.graph.is_empty_node(node_id) + } + + #[inline] + fn has_edge(&self, source: usize, target: usize) -> Result<bool, GError> { + self.graph.has_edge(source, target) + } + + fn replace_by_builder(&mut self, _builder: impl graph::Builder<Result = Self>) { + unimplemented!() + } +} + +impl<T: GraphLabel> ParentsGraph for DefaultForest<T> { + type Iter<'a>= <PLGraph<T> as ParentsGraph>::Iter<'a> + where + Self:'a; + + #[inline] + fn parents_of(&self, node_id: usize) -> Result<<Self as ParentsGraph>::Iter<'_>, GError> { + self.graph.parents_of(node_id) + } + + #[inline] + fn nth_child(&self, node_id: usize, n: usize) -> Result<usize, GError> { + self.graph.nth_child(node_id, n) + } + + #[inline] + fn edge_to_parent( + &self, + source: usize, + target: usize, + ) -> Result<Option<graph::Parent>, GError> { + self.graph.edge_to_parent(source, target) + } +} + +impl<T: GraphLabel> LabelGraph<T> for DefaultForest<T> { + type Iter<'a> = std::iter::Empty<usize> + where + Self: 'a; + + type LabelIter<'a> = std::iter::Empty<(&'a T, <Self as LabelGraph<T>>::Iter<'a>)> + where + Self: 'a, + T: 'a; + + type EdgeLabelIter<'a> = std::iter::Empty<T> + where + Self: 'a, + T: 'a; + + #[inline] + fn query_label(&self, label: T) -> Option<usize> { + self.graph.query_label(label) + } + + #[inline] + fn vertex_label(&self, node_id: usize) -> Result<Option<T>, GError> { + self.graph.vertex_label(node_id) + } + + fn edge_label( + &self, + _source: usize, + _target: usize, + ) -> Result<Self::EdgeLabelIter<'_>, GError> { + unimplemented!("edges have no labels") + } + + fn find_children_with_label( + &self, + _node_id: usize, + _label: &T, + ) -> Result<<Self as LabelGraph<T>>::Iter<'_>, GError> { + unimplemented!("edges have no labels") + } + + fn labels_of(&self, _node_id: usize) -> Result<Self::LabelIter<'_>, GError> { + unimplemented!("edges have no labels") + } + + fn has_edge_label(&self, _node_id: usize, _label: &T, _target: usize) -> Result<bool, GError> { + unimplemented!("edges have no labels") + } +} + +impl<T: GraphLabel> Forest<T> for DefaultForest<ForestLabel<T>> { + type Error = Error; + + fn root(&self) -> Option<usize> { + self.root + } + + fn new_leaf(label: T) -> Self { + let mut graph = PLGraph::default(); + + let mut builder = PLGBuilderMut::from_graph_mut(&mut graph); + + let root = Some(builder.add_vertex(ForestLabel::from(label))); + + Self { graph, root } + } + + fn is_prefix<F>(&self, node_id: usize, fragment: F) -> Result<bool, Self::Error> + where + F: Borrow<Self>, + { + if !self.has_node(node_id) { + return Err(Error::IndexOutOfBounds(node_id, self.nodes_len())); + } + + // We do a depth-first traversal to determine if every node + // encountered has the same set of children (labels taken into + // the consideration). + + let fragment = fragment.borrow(); + + let mut frag_stack = Vec::with_capacity(fragment.nodes_len()); + + let mut self_stack = Vec::with_capacity(fragment.nodes_len()); + + let frag_root = if let Some(root) = fragment.root() { + root + } else { + // an empty forest is a prefix of any forest. + return Ok(true); + }; + + frag_stack.push(frag_root); + self_stack.push(node_id); + + // defer popping + while let (Some(frag_top), Some(self_top)) = + (frag_stack.last().copied(), self_stack.last().copied()) + { + frag_stack.pop(); + self_stack.pop(); + + if fragment.vertex_label(frag_top)? != self.vertex_label(self_top)? { + // not a prefix + return Ok(false); + } + + let mut self_children = self.children_of(self_top)?; + + for child in fragment.children_of(frag_top)? { + if let Some(self_child) = self_children.next() { + frag_stack.push(child); + self_stack.push(self_child); + } else { + // too few children + return Ok(false); + } + } + } + + // Check both stacks are empty at the end. + Ok(frag_stack.is_empty() && self_stack.is_empty()) + } + + fn plant<F>(&mut self, node_id: usize, fragment: F, planted: bool) -> Result<(), Self::Error> + where + F: Borrow<Self>, + { + // Convert self to a builder_mut, and traverse fragment in a + // depth-first manner and adjoin corresponding nodes along the + // way. + + if !self.has_node(node_id) { + return Err(Error::IndexOutOfBounds(node_id, self.nodes_len())); + } + + let fragment = fragment.borrow(); + + let mut builder = PLGBuilderMut::from_graph_mut(&mut self.graph); + + let root = if let Some(root) = fragment.root() { + root + } else { + // Nothing to do to plant an empty forest. + return Ok(()); + }; + + // Just a dummy label for use in adding edges. + // + // REVIEW: I probably should refactor the API for builder_mut. + let root_label = fragment + .vertex_label(root)? + .ok_or(Error::NodeNoLabel(root))?; + + let nodes_len = fragment.nodes_len(); + + /// If the fragment root has a duplicate label, the forest + /// will not grow, so we use the label to find the adjoined + /// node index. + /// + /// The nodes hava already been added to the forest, so it is + /// safe to call unwrap. + macro_rules! conversion ( + ($node:expr) => { + { + builder + .query_label( + fragment + .vertex_label($node)? + .ok_or(Error::NodeNoLabel($node))? + ).unwrap() + } + } + ); + + // If the fragment has been planted before, we just add an + // edge. + + if planted { + builder.add_edge(node_id, conversion!(root), root_label)?; + + return Ok(()); + } + + // First adjoin those nodes and join the edges later. + + for node in 0..nodes_len { + let label = fragment + .vertex_label(node)? + .ok_or(Error::NodeNoLabel(node))?; + + builder.add_vertex(label); + } + + // Don't forget to join the new sub-forest to the original + // forest, at the specified position. + + builder.add_edge(node_id, conversion!(root), root_label)?; + + // We can try to calculate the depth of fragments, if we need + // to lower the memory usage. But in our use cases, we + // usually deal with fragments where each node has at most one + // child, so the depth is supposed to be equal to the length + // in this case. + let mut stack = Vec::with_capacity(fragment.nodes_len()); + + stack.push(root); + + while let Some(top) = stack.pop() { + for child in fragment.children_of(top)? { + builder.add_edge(conversion!(top), conversion!(child), root_label)?; + } + } + + Ok(()) + } + + fn clone_node(&mut self, node_id: usize) -> Result<usize, Self::Error> { + let builder = PLGBuilderMut::from_graph_mut(&mut self.graph); + + let old_label = builder + .vertex_label(node_id)? + .ok_or(Error::NodeNoLabel(node_id))?; + + if old_label.is_packed() { + return Err(ForestLabelError::ClonePack.into()); + } + + // We are sure old_label is not packed here, so it is safe to + // unwrap. + let new_label = old_label.clone(self).unwrap(); + + if old_label.clone_index().is_some() { + let mut parents = self.parents_of(node_id)?; + + // Make sure it only has one parent, which is the + // representative node. + assert_eq!(parents.len(), 1); + + let rep_node = parents.next().unwrap().node(); + + let mut builder = PLGBuilderMut::from_graph_mut(&mut self.graph); + + let new_clone = builder.add_vertex(new_label); + + builder.add_edge(rep_node, new_clone, new_label)?; + + // We checked its length is 1, so it is safe to unwrap + // here. + return Ok(new_clone); + } + + let mut builder = PLGBuilderMut::from_graph_mut(&mut self.graph); + + // We are sure old_label is not a clone here, so it is safe to + // unwrap. + let rep_label = old_label.pack().unwrap(); + + // Make a new node + let new_index = builder.add_vertex(rep_label); + + // Re-direct parents to the new node. + // + // This must be done before pointing the new node to the old + // node, otherwise that edge will be redirected as well. + + // Unfortunately I cannot loop through parents and mutate them + // at the same time, so I first collect them into a vector. + let parents: Vec<_> = builder.parents_of(node_id)?.collect(); + + for parent in parents.into_iter() { + builder.redirect(parent.node(), parent.edge(), new_index)?; + } + + // Point the new node to the old node. OLD_LABEL is just a + // place holder. + + builder.add_edge(new_index, node_id, old_label)?; + + // Modify the label of the old node. + + builder.set_label(node_id, new_label)?; + + // Make another clone + + // new_label is cloned, so is guaranteed not to be packed, and + // we are safe to unwrap. + let new_label = new_label.clone(self).unwrap(); + + let mut builder = PLGBuilderMut::from_graph_mut(&mut self.graph); + + let new_clone = builder.add_vertex(new_label); + + builder.add_edge(new_index, new_clone, new_label)?; + + Ok(new_clone) + } +} + +#[cfg(test)] +mod item_test { + use super::*; + + macro_rules! leaf ( + ($label:expr, $type:tt) =>{ + DefaultForest::<ForestLabel<$type>>::new_leaf($label) + }; + ($label:expr) => { + DefaultForest::<ForestLabel<usize>>::new_leaf($label) + } + ); + + #[test] + fn test_forest_api() -> Result<(), Box<dyn std::error::Error>> { + let forest: DefaultForest<usize> = Default::default(); + + // empty forest + + assert!(forest.is_empty()); + + // leaf forest + + let mut forest = leaf!(0, usize); + + assert_eq!(forest.nodes_len(), 1); + assert_eq!(forest.root(), Some(0)); + + // add some child + + forest.plant(0, leaf!(1), false)?; + + assert_eq!(forest.nodes_len(), 2); + let mut children = forest.children_of(0)?; + assert_eq!(children.next(), Some(1)); + assert_eq!(children.next(), None); + + // add more children + + forest.plant(0, leaf!(2), false)?; + forest.plant(0, leaf!(3), false)?; + forest.plant(0, leaf!(4), false)?; + forest.plant(2, leaf!(5), false)?; + + assert_eq!(forest.nodes_len(), 6); + let mut children = forest.children_of(0)?; + assert_eq!(children.next(), Some(1)); + assert_eq!(children.next(), Some(2)); + assert_eq!(children.next(), Some(3)); + assert_eq!(children.next(), Some(4)); + let mut children = forest.children_of(2)?; + assert_eq!(children.next(), Some(5)); + assert_eq!(children.next(), None); + + let mut test_forest = leaf!(0); + test_forest.plant(0, leaf!(1), false)?; + test_forest.plant(0, leaf!(2), false)?; + test_forest.plant(0, leaf!(3), false)?; + test_forest.plant(2, leaf!(5), false)?; + + assert!(forest.is_prefix(0, &test_forest)?); + + let mut test_forest = leaf!(0); + test_forest.plant(0, leaf!(1), false)?; + test_forest.plant(0, leaf!(2), false)?; + // this child of the root should have label 3 in order to be a + // prefix. + test_forest.plant(0, leaf!(4), false)?; + test_forest.plant(2, leaf!(5), false)?; + + assert!(!forest.is_prefix(0, &test_forest)?); + + let mut test_forest = leaf!(2); + test_forest.plant(0, leaf!(5), false)?; + + assert!(forest.is_prefix(2, &test_forest)?); + + // now test cloning + + // add a duplicate label + forest.plant(3, leaf!(5), false)?; + + let _len = forest.nodes_len(); + + forest.clone_node(5)?; + + assert_eq!(forest.nodes_len(), 7); + + #[cfg(feature = "test-print-viz")] + forest.print_viz("forest.gv")?; + + Ok(()) + } +} diff --git a/chain/src/item/genins.rs b/chain/src/item/genins.rs new file mode 100644 index 0000000..99d9202 --- /dev/null +++ b/chain/src/item/genins.rs @@ -0,0 +1,231 @@ +//! This module implements the generation and insertion of item +//! derivation forests. +//! +//! This is used for the chain-rule machine to conveniently produce +//! item derivations into a forest. This forest can serve as a rough +//! approximation of the parse forests, and can be executed in other +//! semirings later on. + +use super::*; +use crate::{atom::DefaultAtom, default::Error, item::default::DefaultForest, Edge}; +use grammar::{Error as GrammarError, GrammarLabel, GrammarLabelType, TNT}; +use graph::Graph; + +use core::borrow::Borrow; +use std::collections::HashSet as Set; + +/// A helper function to generate a fragment of forest. +/// +/// It simply constructs a root node and then appends +/// successive nodes as successive children of the previous +/// node. Also the starting positions will all be set to the +/// same position. +/// +/// If the input is empty, this returns an empty forest; +/// otherwise the result is not empty. +pub fn generate_fragment( + labels: impl AsRef<[GrammarLabelType]>, + pos: usize, +) -> Result<DefaultForest<ForestLabel<GrammarLabel>>, crate::default::Error> { + let mut labels_iter = labels.as_ref().iter(); + let mut result: DefaultForest<ForestLabel<GrammarLabel>>; + + if let Some(first_label) = labels_iter.next() { + result = DefaultForest::new_leaf(GrammarLabel::new(*first_label, pos)); + + let mut index = 0; + + for label in labels_iter { + result.plant( + index, + DefaultForest::new_leaf(GrammarLabel::new(*label, pos)), + false, + )?; + + // To prevent duplication of labels causing + // panics, we query the index of the new node. + index = result + .query_label(GrammarLabel::new(*label, pos).into()) + // REVIEW: Perhaps a LabelNoNode error? + .ok_or(Error::Invalid)?; + } + } else { + result = Default::default(); + } + + Ok(result) +} + +impl DefaultForest<ForestLabel<GrammarLabel>> { + /// Insert an item derivation forest into a recording forest. + /// + /// We need the help of other things just for finding the correct + /// places to insert these item fragments. + pub fn insert_item( + &mut self, + label: Edge, + fragment: impl Borrow<DefaultForest<ForestLabel<GrammarLabel>>>, + atom_child_iter: impl Iterator<Item = usize>, + atom: &DefaultAtom, + ) -> Result<PaSe, Error> { + /// Convert an error telling us that an index is out of bounds. + /// + /// # Panics + /// + /// The function panics if the error is not of the expected + /// kind. + fn index_out_of_bounds_conversion(ge: GrammarError) -> Error { + match ge { + GrammarError::IndexOutOfBounds(index, bound) => { + Error::IndexOutOfBounds(index, bound) + } + _ => Error::Invalid, + } + } + + let fragment = fragment.borrow(); + + let pase = label.forest_source(); + + let parents: Vec<Parent> = { + let mut result = Vec::new(); + + if let Some(parent) = pase.parent() { + result.push(parent); + } else { + let (root, leaf) = pase.segment().unwrap(); + let mut seen_nodes = Set::new(); + + let mut stack = vec![root]; + + while let Some(top) = stack.pop() { + if seen_nodes.contains(&top) { + continue; + } + + seen_nodes.insert(top); + + for (index, child) in self.children_of(top)?.enumerate() { + if child == leaf { + result.push(Parent::new(top, index)); + } else { + stack.push(child); + } + } + } + } + + result + }; + + for atom_child in atom_child_iter { + // Find reduction information. + let reduction_info = atom + .query_reduction(label.label(), atom_child) + .map_err(index_out_of_bounds_conversion)?; + + let mut stack = parents.clone(); + let mut second_stack = Vec::new(); + + // locate the nodes + for reduction_nt in reduction_info.iter().copied().flatten().rev() { + while let Some(node) = stack.pop() { + // REVIEW: A lot of labels appear here. + // Perhaps I need to refactor something? + if matches!( + self + .vertex_label(node.node())? + .ok_or_else(|| Error::NodeNoLabel(node.node()))? + .label() + .label(), + GrammarLabelType::TNT(TNT::Non(nt)) if nt == *reduction_nt + ) { + for parent in self.parents_of(node.node())? { + debug_assert!(matches!( + self.vertex_label(parent.node()), + Ok(Some(label)) if + label + .label() + .label() + .rule() + .is_some())); + + second_stack.extend(self.parents_of(parent.node())?.filter(|n| { + matches!(self.vertex_label(n.node()), + Ok(Some(label)) + if matches!( + label.label().label().tnt(), + Some(TNT::Non(_)))) + })); + } + } + } + + std::mem::swap(&mut stack, &mut second_stack); + + if stack.is_empty() { + break; + } + } + + if stack.is_empty() { + return Err(Error::CannotPlant); + } + + for parent in stack.into_iter() { + if parent.edge() + 1 >= self.degree(parent.node())? { + self.plant(parent.node(), fragment, false)?; + } else { + let nth_child = self.nth_child(parent.node(), parent.edge() + 1)?; + + if self.is_prefix(nth_child, fragment)? { + // do nothing + continue; + } + + let cloned_node = self.clone_node(nth_child)?; + + self.plant(cloned_node, fragment, false)?; + } + } + } + + let result = if fragment.nodes_len() == 2 { + let root_label = fragment.vertex_label(0)?.unwrap(); + let leaf_label = fragment.vertex_label(1)?.unwrap(); + + // it has been planted, so should be safe. + let node = self.query_label(root_label).unwrap(); + + let edge = { + let mut result = None; + + for (index, child) in self.children_of(node)?.enumerate() { + if matches!(self.vertex_label(child)?, Some(child_label) if child_label == leaf_label) + { + result = Some(index); + break; + } + } + + if let Some(result) = result { + result + } else { + unreachable!("the forest is wrongly planted"); + } + }; + + PaSe::Parent(node, edge) + } else { + let root_label = fragment.vertex_label(0)?.unwrap(); + let leaf_label = fragment.vertex_label(fragment.nodes_len() - 1)?.unwrap(); + + PaSe::Segment( + self.query_label(root_label).unwrap(), + self.query_label(leaf_label).unwrap(), + ) + }; + + Ok(result) + } +} diff --git a/chain/src/item/mod.rs b/chain/src/item/mod.rs new file mode 100644 index 0000000..7fafcc8 --- /dev/null +++ b/chain/src/item/mod.rs @@ -0,0 +1,252 @@ +#![warn(missing_docs)] +//! This module implements the type of items for the chain-rule +//! machine. +//! +//! More specifically, it implements the iten derivation forests for +//! the machine. + +// TODO: Implement an enumeration for Parent or Segment, perhaps +// called PaSe. + +// TODO: Move functions for handling forests, currently contained +// within the method derive to this module, and make them aware of the +// enumeration PaSe. + +// TODO: Implement the Item trait from semirings for the item +// derivation forest, and then we can easily execute items later on. + +use graph::{error::Error as GError, GraphLabel, LabelGraph, Parent, ParentsGraph}; + +use core::borrow::Borrow; + +/// A parent or a segment. +/// +/// A parent is a node with an edge index, which represents a certain +/// edge. +/// +/// A segment represents every edge from the root node to the single +/// terminating node. +#[allow(unused)] +#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)] +pub enum PaSe { + /// An edge from a node, as the n-th child. + Parent(usize, usize), + /// A segment from a root to the single terminating node. + Segment(usize, usize), +} + +impl From<Parent> for PaSe { + fn from(value: Parent) -> Self { + Self::Parent(value.node(), value.edge()) + } +} + +impl Default for PaSe { + fn default() -> Self { + Self::Segment(0, 0) + } +} + +impl core::fmt::Display for PaSe { + fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { + match self { + Self::Parent(node, edge) => write!(f, "the {edge}-th edge from {node}"), + Self::Segment(root, leaf) => write!(f, "a segment from {root} to {leaf}"), + } + } +} + +impl PaSe { + fn parent(self) -> Option<Parent> { + if let Self::Parent(node, edge) = self { + Some(Parent::new(node, edge)) + } else { + None + } + } + + fn segment(self) -> Option<(usize, usize)> { + if let Self::Segment(root, leaf) = self { + Some((root, leaf)) + } else { + None + } + } +} + +/// An internal type that indicates the status of a node as either a +/// packed, cloned, or plain node. +#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Default)] +enum ForestLabelType { + Packed, + #[default] + Plain, + Cloned(usize), +} + +impl core::fmt::Display for ForestLabelType { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + match self { + Self::Packed => write!(f, "packed"), + Self::Plain => write!(f, "plain"), + Self::Cloned(index) => write!(f, "the {index}-th clone"), + } + } +} + +/// A type that encodes the properties demanded by a forest. +#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)] +pub struct ForestLabel<T: GraphLabel> { + label: T, + status: ForestLabelType, +} + +impl<T: GraphLabel> core::fmt::Display for ForestLabel<T> { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + writeln!(f, "label: {}, status: {}", self.label, self.status) + } +} + +/// The type of erros for converting forest labels. +#[non_exhaustive] +#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq)] +pub enum ForestLabelError { + /// Try to pack a cloned node. + PackClone, + /// Try to clone a packed node. + ClonePack, +} + +impl core::fmt::Display for ForestLabelError { + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + match self { + Self::PackClone => write!(f, "cannot pack a cloned node"), + Self::ClonePack => write!(f, "cannot clone a packed node"), + } + } +} + +impl std::error::Error for ForestLabelError {} + +impl<T: GraphLabel> ForestLabel<T> { + /// Retrieve the label. + pub fn label(&self) -> T { + self.label + } + + /// Return true if and only if this node is packed. + pub fn is_packed(&self) -> bool { + matches!(self.status, ForestLabelType::Packed) + } + + /// Retrieve the optional clone index. + pub fn clone_index(&self) -> Option<usize> { + match self.status { + ForestLabelType::Cloned(index) => Some(index), + _ => None, + } + } + + /// Try to clone a node. + pub fn clone<F>(self, forest: &F) -> Result<Self, ForestLabelError> + where + F: Forest<T>, + { + if self.is_packed() { + Err(ForestLabelError::ClonePack) + } else { + let clone_index = if let Some(old_index) = self.clone_index() { + let mut new_index: usize = old_index + 1; + + let mut new_label = Self { + status: ForestLabelType::Cloned(new_index), + ..self + }; + + while forest.query_label(new_label).is_some() { + new_index += 1; + new_label = Self { + status: ForestLabelType::Cloned(new_index), + ..self + }; + } + + new_index + } else { + 0 + }; + + Ok(Self { + status: ForestLabelType::Cloned(clone_index), + ..self + }) + } + } + + /// Try to pack a node. + pub fn pack(self) -> Result<Self, ForestLabelError> { + if self.clone_index().is_some() { + Err(ForestLabelError::PackClone) + } else { + let new_label = Self { + status: ForestLabelType::Packed, + ..self + }; + + Ok(new_label) + } + } +} + +impl<T: GraphLabel> From<T> for ForestLabel<T> { + fn from(label: T) -> Self { + let status = ForestLabelType::default(); + Self { label, status } + } +} + +/// The expected behaviours of an item derivation forest. +/// +/// Note that it requires only a subset of the functionalities of +/// labelled graphs. +pub trait Forest<T: GraphLabel>: ParentsGraph + LabelGraph<ForestLabel<T>> { + /// The type of errors for operations on the forest. + type Error: std::error::Error + From<GError> + From<ForestLabelError>; + + /// Return the root of the forest. + /// + /// A forest without a root is regarded as empty. + fn root(&self) -> Option<usize>; + + /// Construct a forest consisting of one leaf node with the given + /// label. + fn new_leaf(label: T) -> Self; + + /// Detect if the fragment is a prefix of the sub-forest rooted at + /// `node_id`. + fn is_prefix<F>(&self, node_id: usize, fragment: F) -> Result<bool, Self::Error> + where + F: Borrow<Self>; + + /// Extend the forest by adjoining another forest at a given node. + fn plant<F>(&mut self, node_id: usize, fragment: F, planted: bool) -> Result<(), Self::Error> + where + F: Borrow<Self>; + + /// Clone a node by making a new node and making all the nodes + /// that previously pointed to the old node now point to the new + /// node, and the new node points to the old node. Return the + /// index of the new node. In addition, if the old node had + /// already been cloned, just return the index of its + /// representative. + /// + /// The labels of the representing node and of the cloned node + /// will be handled automatically. + fn clone_node(&mut self, node_id: usize) -> Result<usize, Self::Error>; +} + +pub mod default; + +pub mod genins; + +pub use genins::generate_fragment; |