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Diffstat (limited to 'chain/src/grammar.rs')
-rw-r--r-- | chain/src/grammar.rs | 1247 |
1 files changed, 0 insertions, 1247 deletions
diff --git a/chain/src/grammar.rs b/chain/src/grammar.rs deleted file mode 100644 index 287fbca..0000000 --- a/chain/src/grammar.rs +++ /dev/null @@ -1,1247 +0,0 @@ -#![warn(missing_docs)] -//! This file implements the extected behaviours of grammars. - -// NOTE: We shall first start with a parser that works at the level of -// characters. The purpose is to first experiment with the workings -// and the performance of the algorithms, before optimising by using -// regular expressions to classify inputs into tokens. In other -// words, the current focus is not on the optimisations, whereas -// scanners are for optimisations only, so to speak. - -#![allow(unused_imports)] -use nfa::{ - default::{ - nfa::DefaultNFA, - regex::{DefaultRegParser, DefaultRegex, ParseDirection, ParseError, RegexType}, - }, - DOption, DesRec, Nfa, Regex, SoC, -}; - -use graph::{adlist::ALGBuilder, builder::Builder, Graph}; - -use std::{ - collections::HashSet, - fmt::{Display, Write}, -}; - -/// The type of a terminal. -/// -/// For the time being this is a wrapper around a string, but in the -/// future it may hold more information of scanners. -#[derive(Debug, Clone, Eq, PartialEq)] -pub struct Terminal { - // If we want to use scanners, per chance add them as a new field - // here. - name: String, -} - -impl Terminal { - /// Create a terminal with the given name. - #[inline] - pub fn new(name: String) -> Self { - Self { name } - } - - /// Return the name of the terminal. - #[inline] - pub fn name(&self) -> &str { - &self.name - } -} - -/// The type of a non-terminal. -/// -/// This is just a wrapper around a string. -#[derive(Debug, Clone)] -pub struct Nonterminal(String); - -impl Nonterminal { - /// Return the name of the nonterminal. - /// - /// Just to improve readability. - #[inline] - pub fn name(&self) -> &str { - &self.0 - } -} - -/// The type of a terminal or a non-terminal. -/// -/// Only an index is stored here. Actual data are stored in two other -/// arrays. -#[derive(Debug, Hash, Eq, PartialEq, Clone, Copy, Ord, PartialOrd)] -pub enum TNT { - /// Terminal variant - Ter(usize), - /// Nonterminal variant - Non(usize), -} - -impl Display for TNT { - fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { - match self { - TNT::Ter(t) => write!(f, "T({t})"), - TNT::Non(n) => write!(f, "N({n})"), - } - } -} - -/// Errors related to grammar operations. -#[derive(Debug, Copy, Clone)] -#[non_exhaustive] -pub enum Error { - /// The first component is the index, and the second the bound. - IndexOutOfBounds(usize, usize), - /// Fail to build the N-th regular expression, due to the - /// ParseError. - BuildFail(usize, ParseError), - /// fail to build NFA - NFAFail(nfa::error::Error), -} - -impl From<nfa::error::Error> for Error { - fn from(nfae: nfa::error::Error) -> Self { - Self::NFAFail(nfae) - } -} - -impl Display for Error { - fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { - match self { - Error::IndexOutOfBounds(i, b) => write!(f, "index {i} out of bound {b}"), - Error::BuildFail(n, pe) => write!( - f, - "Failed to build the {n}-th regular expression due to error: {pe}" - ), - Error::NFAFail(nfae) => write!(f, "failed to build NFA because of {nfae}"), - } - } -} - -impl std::error::Error for Error {} - -/// A rule is a regular expression of terminals or non-terminals. -#[derive(Debug, Clone)] -pub struct Rule { - regex: DefaultRegex<TNT>, -} - -impl Rule { - /// Return true if and only if the rule is empty. - #[inline] - pub fn is_empty(&self) -> bool { - self.regex.is_empty() - } - - /// Return the length of the rule. - #[inline] - pub fn len(&self) -> usize { - self.regex.len() - } -} - -/// The type of a grammar. -#[derive(Debug, Clone, Default)] -pub struct Grammar { - ter: Vec<Terminal>, - non: Vec<Nonterminal>, - rules: Vec<Rule>, - firsts: Vec<HashSet<Option<usize>>>, - first_nodes: Vec<Vec<usize>>, -} - -/// A private type to aid the recursive looping of rergular -/// expressions. -#[derive(Copy, Clone)] -enum StackElement { - Seen(usize), - Unseen(usize), -} - -impl StackElement { - fn index(self) -> usize { - match self { - Self::Seen(index) => index, - Self::Unseen(index) => index, - } - } - - fn is_seen(self) -> bool { - matches!(self, Self::Seen(_)) - } -} - -impl Grammar { - /// Construct a grammar from a vector of terminals, a vector of - /// non-terminals, and a vector of rules for the non-temrinals. - /// - /// # Panic - /// - /// If the length of `non` is not equal to that of `rules`, then - /// the function panics. - pub fn new(ter: Vec<Terminal>, non: Vec<Nonterminal>, rules: Vec<Rule>) -> Self { - assert_eq!(non.len(), rules.len()); - - // One more room is reserved for the `None` value. - let firsts = std::iter::repeat_with(|| HashSet::with_capacity(ter.len() + 1)) - .take(non.len()) - .collect(); - - let first_nodes = rules - .iter() - .map(|rule| Vec::with_capacity(rule.len())) - .collect(); - - Self { - ter, - non, - rules, - firsts, - first_nodes, - } - } - - /// Return the name of a terminal or a non-terminal. - pub fn name_of_tnt(&self, tnt: TNT) -> Result<String, Error> { - match tnt { - TNT::Ter(t) => Ok(format!( - "T{}", - self.ter - .get(t) - .ok_or(Error::IndexOutOfBounds(t, self.ter.len()))? - .name() - )), - TNT::Non(n) => Ok(format!( - "N{}", - self.non - .get(n) - .ok_or(Error::IndexOutOfBounds(n, self.non.len()))? - .name() - )), - } - } - - /// Return true if and only if there are no non-terminals in the - /// grammar. - #[inline] - pub fn is_empty(&self) -> bool { - self.non.is_empty() - } - - /// Return the total length of all rules. - #[inline] - pub fn total(&self) -> usize { - self.rules.iter().map(Rule::len).sum() - } - - /// Return the number of terminals. - #[inline] - pub fn ter_num(&self) -> usize { - self.ter.len() - } - - /// Return the number of non-terminals. - #[inline] - pub fn non_num(&self) -> usize { - self.non.len() - } - - /// Convert a non-terminal `N` to `N + TER_NUM`, so that we use a - /// single number to represent terminals and non-terminals. - /// - /// # Bounds - /// - /// If a terminal index is greater than or equal to the number of - /// terminals, then this signals an error; mutatis mutandis for - /// non-terminals. - /// - /// # Related - /// - /// The inverse function is [`unpack_tnt`][Grammar::unpack_tnt]. - #[inline] - pub fn pack_tnt(&self, tnt: TNT) -> Result<usize, Error> { - let ter_num = self.ter.len(); - let non_num = self.non.len(); - - match tnt { - TNT::Ter(t) => { - if t >= ter_num { - Err(Error::IndexOutOfBounds(t, ter_num)) - } else { - Ok(t) - } - } - TNT::Non(n) => { - if n >= non_num { - Err(Error::IndexOutOfBounds(n, non_num)) - } else { - Ok(n + ter_num) - } - } - } - } - - /// Convert a single number to either a terminal or a - /// non-terminal. - /// - /// # Bounds - /// - /// If the number is greater than or equal to the sum of the - /// numbers of terminals and of non-terminals, then this signals - /// an error. - /// - /// # Related - /// - /// This is the inverse of [`pack_tnt`][Grammar::pack_tnt]. - #[inline] - pub fn unpack_tnt(&self, flat: usize) -> Result<TNT, Error> { - let ter_num = self.ter.len(); - let non_num = self.non.len(); - - if flat < ter_num { - Ok(TNT::Ter(flat)) - } else if flat < ter_num + non_num { - Ok(TNT::Non(flat - ter_num)) - } else { - Err(Error::IndexOutOfBounds(flat, ter_num + non_num)) - } - } - - /// Return true if and only if the non-terminal is nullable. - #[inline] - pub fn is_nullable(&self, non_terminal: usize) -> Result<bool, Error> { - Ok(self - .firsts - .get(non_terminal) - .ok_or(Error::IndexOutOfBounds(non_terminal, self.non.len()))? - .contains(&None)) - } - - /// For a NON_TERMINAL, return an iterator that goes over the - /// nodes that are reachable from the non-terminal through an - /// empty transition of the nondeterministic finite automaton. - #[inline] - pub fn first_nodes_of(&self, non_terminal: usize) -> Result<std::slice::Iter<usize>, Error> { - Ok(self - .first_nodes - .get(non_terminal) - .ok_or(Error::IndexOutOfBounds(non_terminal, self.non.len()))? - .iter()) - } - - /// Compute the set of terminals that can appear as the first - /// terminal in some left-linear derivation of a non-terminal, for - /// every non-terminal. - /// - /// This is an algorithm that computes the transitive closure, - /// which is a common approach for this task. But perhaps there - /// are more efficient approaches? - /// - /// Also the function computes the set of "reachable nodes" in the - /// process, and records the information in the `first_nodes` - /// attribute. - pub fn compute_firsts(&mut self) -> Result<(), Error> { - let mut updated = true; - - let non_len = self.non_num(); - - use StackElement::{Seen, Unseen}; - - while updated { - updated = false; - - for (n, regex) in self.rules.iter().map(|rule| &rule.regex).enumerate() { - let root = if let Some(root) = regex.root() { - root - } else { - if !self.is_nullable(n)? { - updated = true; - - self.firsts.get_mut(n).unwrap().insert(None); - - // The default construction of a grammar - // reserves some space for each vector, so - // explicitly setting this can reduce some - // minor memory overhead. - let pointer = self.first_nodes.get_mut(n).unwrap(); - - pointer.clear(); - pointer.shrink_to_fit(); - } - - continue; - }; - - let regex_len = regex.len(); - - let mut stack: Vec<StackElement> = Vec::with_capacity(regex_len); - - stack.push(Unseen(root)); - - let mut children_sets_stack: Vec<HashSet<Option<usize>>> = - Vec::with_capacity(regex_len); - - let mut children_nodes_stack: Vec<HashSet<usize>> = Vec::with_capacity(regex_len); - - while let Some(top) = stack.pop() { - let top_index = top.index(); - let is_seen = top.is_seen(); - - match regex - .vertex_label(top_index) - .map_err(|_| Error::IndexOutOfBounds(top_index, regex_len))? - { - RegexType::Kleene => { - if !is_seen { - stack.push(Seen(top_index)); - - for child in regex.children_of(top_index).unwrap() { - stack.push(Unseen(child)); - } - } else { - let degree = regex.degree(top_index).unwrap(); - let children_stack_len = children_sets_stack.len(); - let children_nodes_len = children_nodes_stack.len(); - - assert!( - children_stack_len >= degree, - "not enough stack elements for {top_index}" - ); - - assert!( - children_nodes_len >= degree, - "not enough stack elements for {top_index}" - ); - - let mut this_set = HashSet::new(); - - this_set.insert(None); - - let mut this_nodes = HashSet::new(); - - this_nodes.insert(top_index); - - if degree == 0 { - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - - continue; - } - - let mut stop = false; - - for (child_set, child_nodes) in children_sets_stack - .drain((children_stack_len - degree)..) - .zip( - children_nodes_stack.drain((children_nodes_len - degree)..), - ) - { - if stop { - break; - } - - if !child_set.contains(&None) { - stop = true; - } - - this_set.extend(child_set); - this_nodes.extend(child_nodes); - } - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - } - } - RegexType::Plus => { - if !is_seen { - stack.push(Seen(top_index)); - - for child in regex.children_of(top_index).unwrap() { - stack.push(Unseen(child)); - } - } else { - let degree = regex.degree(top_index).unwrap(); - let children_stack_len = children_sets_stack.len(); - let children_nodes_len = children_nodes_stack.len(); - - assert!( - children_stack_len >= degree, - "not enough stack elements for {top_index}" - ); - - assert!( - children_nodes_len >= degree, - "not enough stack elements for {top_index}" - ); - - let mut this_set = HashSet::new(); - - let mut this_nodes = HashSet::new(); - - this_nodes.insert(top_index); - - if degree == 0 { - this_set.insert(None); - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - - continue; - } - - let mut stop = false; - - for (child_set, child_nodes) in children_sets_stack - .drain((children_stack_len - degree)..) - .zip( - children_nodes_stack.drain((children_nodes_len - degree)..), - ) - { - if stop { - break; - } - - if !child_set.contains(&None) { - stop = true; - } - - this_set.extend(child_set); - this_nodes.extend(child_nodes); - } - - if stop { - this_set.remove(&None); - } - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - } - } - RegexType::Optional => { - if !is_seen { - stack.push(Seen(top_index)); - - for child in regex.children_of(top_index).unwrap() { - stack.push(Unseen(child)); - } - } else { - let degree = regex.degree(top_index).unwrap(); - let children_stack_len = children_sets_stack.len(); - let children_nodes_len = children_nodes_stack.len(); - - assert!( - children_stack_len >= degree, - "not enough stack elements for {top_index}" - ); - - assert!( - children_nodes_len >= degree, - "not enough stack elements for {top_index}" - ); - - let mut this_set = HashSet::new(); - - this_set.insert(None); - - let mut this_nodes = HashSet::new(); - - this_nodes.insert(top_index); - - if degree == 0 { - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - - continue; - } - - let mut stop = false; - - for (child_set, child_nodes) in children_sets_stack - .drain((children_stack_len - degree)..) - .zip( - children_nodes_stack.drain((children_nodes_len - degree)..), - ) - { - if stop { - break; - } - - if !child_set.contains(&None) { - stop = true; - } - - this_set.extend(child_set.iter().copied()); - this_nodes.extend(child_nodes.iter().copied()); - } - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - } - } - RegexType::Or => { - if !is_seen { - stack.push(Seen(top_index)); - - for child in regex.children_of(top_index).unwrap() { - stack.push(Unseen(child)); - } - } else { - let degree = regex.degree(top_index).unwrap(); - let children_stack_len = children_sets_stack.len(); - let children_nodes_len = children_nodes_stack.len(); - - assert!( - children_stack_len >= degree, - "not enough stack elements for {top_index}" - ); - - assert!( - children_nodes_len >= degree, - "not enough stack elements for {top_index}" - ); - - let mut this_set = HashSet::new(); - - let mut this_nodes = HashSet::new(); - - this_nodes.insert(top_index); - - if degree == 0 { - this_set.insert(None); - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - - continue; - } - - for (child_set, child_nodes) in children_sets_stack - .drain((children_stack_len - degree)..) - .zip( - children_nodes_stack.drain((children_nodes_len - degree)..), - ) - { - this_set.extend(child_set.iter().copied()); - this_nodes.extend(child_nodes.iter().copied()); - } - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - } - } - RegexType::Paren => { - // Only for printing purposes - let mut this_set = HashSet::new(); - - this_set.insert(None); - - children_sets_stack.push(this_set); - - let mut this_nodes = HashSet::new(); - - this_nodes.insert(top_index); - - children_nodes_stack.push(this_nodes); - } - RegexType::Empty => { - if !is_seen { - stack.push(Seen(top_index)); - - for child in regex.children_of(top_index).unwrap().rev() { - stack.push(Unseen(child)); - } - } else { - let degree = regex.degree(top_index).unwrap(); - let children_stack_len = children_sets_stack.len(); - let children_nodes_len = children_nodes_stack.len(); - - assert!( - children_stack_len >= degree, - "not enough stack elements for {top_index}" - ); - - assert!( - children_nodes_len >= degree, - "not enough stack elements for {top_index}" - ); - - let mut this_set = HashSet::new(); - - let mut this_nodes = HashSet::new(); - - this_nodes.insert(top_index); - - if degree == 0 { - this_set.insert(None); - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - - continue; - } - - let mut stop = false; - - for (child_set, child_nodes) in children_sets_stack - .drain((children_stack_len - degree)..) - .zip( - children_nodes_stack.drain((children_nodes_len - degree)..), - ) - { - if stop { - break; - } - - if !child_set.contains(&None) { - stop = true; - } - - this_set.extend(child_set.iter().copied()); - this_nodes.extend(child_nodes.iter().copied()); - } - - if stop { - this_set.remove(&None); - } - - children_sets_stack.push(this_set); - children_nodes_stack.push(this_nodes); - } - } - RegexType::Lit(tnt) => { - match tnt { - TNT::Ter(t) => { - let mut this_set = HashSet::with_capacity(1); - - this_set.insert(Some(t)); - - children_sets_stack.push(this_set); - } - TNT::Non(non) => { - let this_set = self - .firsts - .get(non) - .ok_or(Error::IndexOutOfBounds(non, non_len))? - .clone(); - - children_sets_stack.push(this_set); - } - } - - let mut this_nodes = HashSet::with_capacity(1); - this_nodes.insert(top_index); - - children_nodes_stack.push(this_nodes); - } - } - } - - assert_eq!( - children_sets_stack.len(), - 1, - "Too many elements left at the end" - ); - - assert_eq!( - children_nodes_stack.len(), - 1, - "Too many elements left at the end" - ); - - for first in children_sets_stack.pop().unwrap().into_iter() { - if !self.firsts.get(n).unwrap().contains(&first) { - updated = true; - - self.firsts.get_mut(n).unwrap().insert(first); - } - } - - *self.first_nodes.get_mut(n).unwrap() = - children_nodes_stack.pop().unwrap().into_iter().collect(); - } - } - - Ok(()) - } - - /// Return the regular language of the left-linear closures of - /// non-terminals in the grammar. - /// - /// The resulting vector is guaranteed to be of the same length as - /// the number of non-terminals. - /// - /// The resulting regular language is not "self-contained". That - /// is to say, its terminals indices are packed indices and are - /// meaningless without the interpretation of the grammar. They - /// should be converted to a nondeterministic finite automaton and - /// then to its null closure later on. - pub fn left_closure(&self) -> Result<Vec<DefaultRegex<TNT>>, Error> { - let non_len = self.non_num(); - - let mut result = Vec::with_capacity(non_len); - - for (n, rule) in self.rules.iter().enumerate() { - let regex = &rule.regex; - - let regex_root = if let Some(root) = regex.root() { - root - } else { - result.push(Default::default()); - - continue; - }; - - let regex_len = regex.len(); - - /// A convenient macro to retrieve the children from the - /// original regular expression with error propagation. - macro_rules! children { - ($n:expr) => { - regex - .children_of($n) - .map_err(|_| Error::IndexOutOfBounds($n, regex_len))? - }; - } - - /// A convenient macro to retrieve the label from the - /// original regular expression with error propagation. - macro_rules! label { - ($n:expr) => { - regex - .vertex_label($n) - .map_err(|_| Error::IndexOutOfBounds($n, regex_len))? - }; - } - - let parents = regex.parents_array().map_err(|e| match e { - nfa::error::Error::UnknownNode(n) => Error::IndexOutOfBounds(n, regex_len), - nfa::error::Error::Cycle => Error::BuildFail(n, ParseError::Cycle), - _ => unreachable!(), - })?; - - use RegexType::*; - use TNT::*; - - let mut local_result: Vec<RegexType<TNT>> = Vec::with_capacity(regex_len * 2); - let mut builder = ALGBuilder::default(); - - /// Perform a depth-first copy - macro_rules! df_copy { - ($parent:expr, $index:expr) => { - match label!($index) { - Kleene | Plus | Optional | Or | Paren | Empty => { - let mut stack = vec![($parent, $index)]; - - while let Some((top_parent, top_index)) = stack.pop() { - let label = label!(top_index); - let label = match label { - Lit(top_tnt) => Lit(Ter(self.pack_tnt(top_tnt).unwrap())), - _ => label, - }; - - local_result.push(label); - - let new = builder.add_vertex(); - - builder.add_edge(top_parent, new, ()).unwrap(); - - stack.extend(children!(top_index).map(|child| (new, child))); - } - } - Lit(remain_tnt) => { - local_result.push(Lit(Ter(self.pack_tnt(remain_tnt).unwrap()))); - let new = builder.add_vertex(); - builder.add_edge($parent, new, ()).unwrap(); - } - } - }; - } - - local_result.push(Or); - builder.add_vertex(); - - local_result.push(Lit(Ter(self.pack_tnt(Non(n)).unwrap()))); - let non_lit_index = builder.add_vertex(); - - builder.add_edge(0, non_lit_index, ()).unwrap(); - - for first_node in self.first_nodes_of(n)?.copied() { - assert!(first_node < parents.len()); - - let tnt = match label!(first_node) { - Lit(tnt) => tnt, - _ => continue, - }; - - let mut parents_chain = { - let mut result = Vec::new(); - let mut stack = Vec::with_capacity(parents.len()); - - stack.push(first_node); - - while let Some(top) = stack.pop() { - assert!(top < parents.len()); - if let Some(parent) = parents.get(top).copied().unwrap() { - result.push(parent); - stack.push(parent.0); - } - } - - result.reverse(); - - result - }; - - if parents_chain.is_empty() { - local_result.push(Lit(tnt)); - let lit_index = builder.add_vertex(); - builder.add_edge(0, lit_index, ()).unwrap(); - - continue; - } - - assert!(parents_chain.first().unwrap().0 == regex_root); - - // A different, "more local", root. - let mut root: usize; - - // Handle the direct parent - let (parent_node, parent_edge_index) = parents_chain.pop().unwrap(); - - match label!(parent_node) { - Kleene | Plus => { - local_result.extend([Empty, Lit(tnt)]); - - root = builder.add_vertex(); - let lit_index = builder.add_vertex(); - builder.add_edge(root, lit_index, ()).unwrap(); - - let iterator = children!(parent_node); - - for index in iterator.clone().skip(parent_edge_index + 1) { - df_copy!(root, index); - } - - local_result.push(Kleene); - let new_parent = builder.add_vertex(); - builder.add_edge(root, new_parent, ()).unwrap(); - - for index in iterator { - df_copy!(new_parent, index); - } - } - - Or => { - local_result.push(Lit(tnt)); - root = builder.add_vertex(); - } - Optional | Empty => { - // If this path is taken, it should not be - // optional. - local_result.extend([Empty, Lit(tnt)]); - root = builder.add_vertex(); - let lit_index = builder.add_vertex(); - builder.add_edge(root, lit_index, ()).unwrap(); - - for index in children!(parent_node).skip(parent_edge_index + 1) { - df_copy!(root, index); - } - } - Paren | Lit(_) => unreachable!(), - } - - // Handle successive parents - - for (node, edge_index) in parents_chain.into_iter() { - let node_type = label!(node); - - match node_type { - Kleene | Plus => { - local_result.push(Empty); - let new_index = builder.add_vertex(); - builder.add_edge(new_index, root, ()).unwrap(); - - root = new_index; - - let iterator = children!(node); - - for index in iterator.clone().skip(edge_index + 1) { - df_copy!(root, index); - } - - local_result.push(Kleene); - let new_parent = builder.add_vertex(); - builder.add_edge(root, new_parent, ()).unwrap(); - - for index in iterator { - df_copy!(new_parent, index); - } - } - RegexType::Or => {} - RegexType::Optional | RegexType::Empty => { - local_result.push(Empty); - let new_index = builder.add_vertex(); - builder.add_edge(new_index, root, ()).unwrap(); - root = new_index; - - for index in children!(node).skip(edge_index + 1) { - df_copy!(root, index); - } - } - RegexType::Paren | RegexType::Lit(_) => unreachable!(), - } - } - - builder.add_edge(0, root, ()).unwrap(); - } - - local_result.shrink_to_fit(); - - let graph = builder.build(); - - assert_eq!(graph.nodes_len(), local_result.len()); - - result.push( - DefaultRegex::new(graph, local_result) - .map_err(|_| Error::BuildFail(n, ParseError::Cycle))?, - ); - } - - assert_eq!(result.len(), non_len); - - Ok(result) - } - - /// Convert the regular language of left-linear closures to its - /// equivalent nondeterministic finite automaton. - /// - /// In the generation of the left-linear closure, the terminals - /// and non-terminals are packed into an unsigned integer. We - /// unpack them in converting to nondeterministic finite - /// automaton. - /// - /// The resulting nondeterministic finite automaton should be - /// transformed to its null-closure for use in our algorithm. - pub fn left_closure_to_nfa( - &self, - closure: &[DefaultRegex<TNT>], - ) -> Result<DefaultNFA<DOption<TNT>>, Error> { - let label_transform = |tnt| match tnt { - TNT::Ter(t) => { - let new_tnt = self.unpack_tnt(t).map_err(|e| match e { - Error::IndexOutOfBounds(index, bound) => { - graph::error::Error::IndexOutOfBounds(index, bound) - } - _ => unreachable!(), - })?; - - Ok(SoC::Carry(new_tnt)) - } - TNT::Non(n) => Ok(SoC::Sub(n)), - }; - - DefaultNFA::to_nfa(closure, label_transform).map_err(Into::into) - } -} - -impl Display for Grammar { - fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { - assert_eq!(self.non.len(), self.rules.len()); - - for (nt, rule) in self.non.iter().zip(self.rules.iter()) { - write!(f, "{}: ", nt.name())?; - - writeln!( - f, - "{}", - rule.regex.to_string_with(|tnt| format!( - "({})", - self.name_of_tnt(tnt) - .unwrap_or_else(|_| format!("Unknown {tnt:?}")) - ))? - )?; - } - - Ok(()) - } -} - -#[cfg(test)] -mod test_grammar_helper { - use super::*; - use nfa::default::regex::{DefaultRegParser, ParseDirection, ParseError, RegexType}; - use std::fmt::Write; - - // Construct a grammar to test - pub fn new_grammar() -> Result<Grammar, Box<dyn std::error::Error>> { - let ter = vec![Terminal::new("a".to_owned()), Terminal::new("b".to_owned())]; - let non = vec![ - Nonterminal("start".to_owned()), - Nonterminal("end".to_owned()), - ]; - - /// A function to scan the inputs. - fn scan_tnt( - parser: &DefaultRegParser<TNT>, - input: &str, - ) -> Result<Option<(usize, RegexType<TNT>, ParseDirection)>, ParseError> { - use ParseDirection::*; - use RegexType::*; - use TNT::*; - - let mut chars = input.chars(); - - if let Some(first) = chars.next() { - match first { - '*' => Ok(Some((1, Kleene, Right))), - '+' => Ok(Some((1, Plus, Right))), - '?' => Ok(Some((1, Optional, Right))), - '|' => Ok(Some((1, Empty, Up))), - '(' => Ok(Some((1, Or, Down))), - ')' => Ok(Some((1, Paren, Up))), - 'T' => { - let mut name = String::new(); - let mut len = 1; - - while let Some(c) = chars.next() { - if ('a'..='z').contains(&c) { - len += 1; - write!(name, "{c}").map_err(|_| ParseError::InvalidCharacter(c))?; - } else { - break; - } - } - - if let Some(t) = parser.query(&name, true) { - Ok(Some((len, Lit(Ter(t)), Right))) - } else { - Err(ParseError::InvalidCharacter(first)) - } - } - 'N' => { - let mut name = String::new(); - let mut len = 1; - - while let Some(c) = chars.next() { - if ('a'..='z').contains(&c) { - len += 1; - write!(name, "{c}").map_err(|_| ParseError::InvalidCharacter(c))?; - } else { - break; - } - } - - if let Some(n) = parser.query(&name, false) { - Ok(Some((len, Lit(Non(n)), Right))) - } else { - Err(ParseError::InvalidCharacter(first)) - } - } - _ => Err(ParseError::InvalidCharacter(first)), - } - } else { - Ok(None) - } - } - - let mut regex_parser: DefaultRegParser<TNT> = Default::default(); - - regex_parser.add_tnt("a", true); - regex_parser.add_tnt("b", true); - regex_parser.add_tnt("start", false); - regex_parser.add_tnt("end", false); - - let regex_parser = regex_parser; - - let rule1 = Rule { - regex: regex_parser - .parse("Ta*Tb+Nend+", Box::new(scan_tnt), true)? - .ok_or(ParseError::Invalid)? - .0, - }; - - let rule2 = Rule { - regex: regex_parser - .parse("Nstart?Nend*", Box::new(scan_tnt), true)? - .ok_or(ParseError::Invalid)? - .0, - }; - - let rules = vec![rule1, rule2]; - - Ok(Grammar::new(ter, non, rules)) - } -} - -#[cfg(test)] -mod test_grammar_display { - use super::test_grammar_helper::new_grammar; - - #[test] - fn test_display() -> Result<(), Box<dyn std::error::Error>> { - println!("{}", new_grammar()?); - - Ok(()) - } -} - -#[cfg(test)] -mod test_grammar_firsts { - use super::test_grammar_helper::new_grammar; - use super::*; - - #[test] - fn test_firsts() -> Result<(), Box<dyn std::error::Error>> { - let mut grammar = new_grammar()?; - - grammar.compute_firsts()?; - - println!("grammar firsts: {:?}", grammar.firsts); - println!("grammar first nodes: {:?}", grammar.first_nodes); - - Ok(()) - } -} - -#[cfg(test)] -mod test_grammar_left_closure { - use super::test_grammar_helper::new_grammar; - use super::*; - - pub fn new_closure_regex( - grammar: &mut Grammar, - ) -> Result<Vec<DefaultRegex<TNT>>, Box<dyn std::error::Error>> { - grammar.compute_firsts()?; - - println!("grammar firsts: {:?}", grammar.firsts); - println!("grammar first nodes: {:?}", grammar.first_nodes); - println!("grammar:"); - println!("{grammar}"); - - grammar.left_closure().map_err(Into::into) - } - - #[test] - fn test_regex() -> Result<(), Box<dyn std::error::Error>> { - let mut grammar = new_grammar()?; - - let vec_of_regexps = new_closure_regex(&mut grammar)?; - - for regex in &vec_of_regexps { - println!("regex: {}", regex.to_string_with(|tnt| format!("{tnt}"))?); - // println!("regex: {regex:?}",); - println!("regex len = {}", regex.nodes_len()); - } - - Ok(()) - } - - #[test] - fn test_nfa() -> Result<(), Box<dyn std::error::Error>> { - let mut grammar = new_grammar()?; - let closure = new_closure_regex(&mut grammar)?; - let nfa = grammar.left_closure_to_nfa(&closure)?; - // TODO: print the nfa out - Ok(()) - } -} |