summaryrefslogtreecommitdiff
path: root/chain/src/atom/default.rs
blob: e88cfc92287bb2e9ed6d83518d6e73cceb4c7362 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
//! This file provides a default implementation of the
//! [`Atom`][super::Atom] trait.

use super::*;
use grammar::Grammar;
use graph::{error::Error as GraphError, Graph, LabelExtGraph, LabelGraph};
use nfa::{
    default::{nfa::DefaultNFA, regex::DefaultRegex},
    LabelType, NfaLabel,
};

use core::fmt::Display;
use std::collections::BTreeMap as Map;

/// A virtual node represents the derivative of a non-terminal symbol
/// `S` with respect to a terminal symbol `t`.
#[derive(Debug, Clone, Copy, Eq, PartialEq, Hash, Ord, PartialOrd)]
struct VirtualNode {
    s: usize,
    t: usize,
}

impl Display for VirtualNode {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "VN[{}]^({})", self.s, self.t)
    }
}

impl VirtualNode {
    fn new(s: usize, t: usize) -> Self {
        Self { s, t }
    }
}

type VirtualMap = Map<VirtualNode, usize>;

/// The type of atomic languages.
#[derive(Debug, Clone, Default)]
pub struct DefaultAtom {
    grammar: Grammar,
    nfa: DefaultNFA<LabelType<TNT>>,
    accepting_vec: Vec<bool>,
    // NOTE: This is mostly for printing and debugging
    regexp: Vec<DefaultRegex<TNT>>,
    virtual_nodes: VirtualMap,
}

impl DefaultAtom {
    /// Return the string description of a rule position.
    pub fn rule_pos_string(&self, pos: usize) -> Result<String, Box<dyn std::error::Error>> {
        let rule_num = self.grammar.get_rule_num(pos)?;

        assert!(rule_num < self.grammar.non_num());

        let display_tnt = |tnt| self.name_of_tnt(tnt).unwrap_or_else(|e| format!("{e}"));

        Ok(self.regexp.get(rule_num).unwrap().to_string_with_dot(
            display_tnt,
            if rule_num == 0 {
                pos
            } else {
                pos - self.grammar.nth_accumulator(rule_num - 1)?
            },
        )?)
    }

    /// Print the underlying NFA.
    pub fn print_nfa<S: AsRef<str>>(&self, filename: S) -> Result<(), std::io::Error> {
        self.nfa.print_viz(filename.as_ref())?;

        let nullables: Vec<_> = self
            .accepting_vec
            .iter()
            .enumerate()
            .filter_map(|(index, pred)| if *pred { Some(index) } else { None })
            .collect();

        if !nullables.is_empty() {
            println!("nullables: {nullables:?}");
        }

        println!("printing virtual nodes:");
        for (vn, node) in self.virtual_nodes.iter() {
            println!("[{}]^{{({})}}: {}", vn.s, vn.t, node);
        }

        Ok(())
    }
}

impl Display for DefaultAtom {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let grammar = &self.grammar;

        let error_to_string = |err| format!("{err}");
        let tnt_to_string = |tnt, deco| {
            grammar
                .name_of_tnt(tnt)
                .map(|name| format!("{deco}({name})"))
                .unwrap_or_else(error_to_string)
        };

        let display_tnt = |tnt| match tnt {
            TNT::Ter(t) => format!(
                "({})",
                grammar
                    .unpack_tnt(t)
                    .map(|tnt| tnt_to_string(tnt, ""))
                    .unwrap_or_else(error_to_string)
            ),
            TNT::Non(_) => tnt_to_string(tnt, "H"),
        };

        writeln!(f, "regular expressions:")?;

        let mut accumulators = Vec::with_capacity(self.regexp.len() + 1);
        accumulators.push(0usize);

        for regex in self.regexp.iter() {
            writeln!(f, "accumulator: {}", accumulators.last().unwrap())?;

            accumulators.push(regex.nodes_len() * 2 + accumulators.last().unwrap());

            let string = regex.to_string_with(display_tnt)?;

            writeln!(f, "{string}")?;
        }

        writeln!(f, "total = {}", accumulators.last().unwrap())?;

        writeln!(f, "virtual nodes:")?;

        for (virtual_node, index) in self.virtual_nodes.iter() {
            writeln!(f, "{virtual_node}: {index}")?;
        }

        Ok(())
    }
}

// Some boiler-plate delegation implementations for Graph and
// LabelGraph, in order to implement Nfa.

impl Graph for DefaultAtom {
    type Iter<'b> = <DefaultNFA<LabelType<TNT>> as Graph>::Iter<'b>
    where
        Self: 'b;

    fn is_empty(&self) -> bool {
        self.nfa.is_empty()
    }

    fn nodes_len(&self) -> usize {
        self.nfa.nodes_len()
    }

    fn children_of(&self, node_id: usize) -> Result<Self::Iter<'_>, GraphError> {
        self.nfa.children_of(node_id)
    }

    fn degree(&self, node_id: usize) -> Result<usize, GraphError> {
        self.nfa.degree(node_id)
    }

    fn is_empty_node(&self, node_id: usize) -> Result<bool, GraphError> {
        self.nfa.is_empty_node(node_id)
    }

    fn has_edge(&self, source: usize, target: usize) -> Result<bool, GraphError> {
        self.nfa.has_edge(source, target)
    }

    fn replace_by_builder(&mut self, _builder: impl graph::Builder<Result = Self>) {
        // NOTE: We cannot replace by a builder whose result is an
        // atom, not the underlying graph type.
        unimplemented!()
    }
}

impl LabelGraph<LabelType<TNT>> for DefaultAtom {
    type Iter<'b> = <DefaultNFA<LabelType<TNT>> as LabelGraph<LabelType<TNT>>>::Iter<'b>
    where
        Self: 'b;

    type LabelIter<'b> = <DefaultNFA<LabelType<TNT>> as LabelGraph<LabelType<TNT>>>::LabelIter<'b>
    where
        Self: 'b,
        DOption<TNT>: 'b;

    type EdgeLabelIter<'a> = <DefaultNFA<LabelType<TNT>> as LabelGraph<LabelType<TNT>>>::EdgeLabelIter<'a>
    where
        Self: 'a,
        DOption<TNT>: 'a;

    #[inline]
    fn vertex_label(&self, node_id: usize) -> Result<Option<LabelType<TNT>>, GraphError> {
        self.nfa.vertex_label(node_id)
    }

    #[inline]
    fn edge_label(
        &self,
        source: usize,
        target: usize,
    ) -> Result<Self::EdgeLabelIter<'_>, GraphError> {
        self.nfa.edge_label(source, target)
    }

    #[inline]
    fn find_children_with_label(
        &self,
        node_id: usize,
        label: &LabelType<TNT>,
    ) -> Result<<Self as LabelGraph<LabelType<TNT>>>::Iter<'_>, GraphError> {
        self.nfa.find_children_with_label(node_id, label)
    }

    #[inline]
    fn labels_of(&self, node_id: usize) -> Result<Self::LabelIter<'_>, GraphError> {
        self.nfa.labels_of(node_id)
    }

    #[inline]
    fn has_edge_label(
        &self,
        node_id: usize,
        label: &LabelType<TNT>,
        target: usize,
    ) -> Result<bool, GraphError> {
        self.nfa.has_edge_label(node_id, label, target)
    }
}

impl LabelExtGraph<LabelType<TNT>> for DefaultAtom {
    #[inline]
    fn extend(
        &mut self,
        edges: impl IntoIterator<Item = (LabelType<TNT>, usize)>,
    ) -> Result<usize, GraphError> {
        self.nfa.extend(edges)
    }
}

impl Nfa<LabelType<TNT>> for DefaultAtom {
    type FromRegex<S: graph::GraphLabel + std::fmt::Display + Default> = ();

    #[inline]
    fn to_nfa(
        _regexps: &[impl nfa::Regex<nfa::default::regex::RegexType<LabelType<TNT>>>],
        _sub_pred: impl Fn(LabelType<TNT>) -> Result<nfa::SoC<LabelType<TNT>>, nfa::error::Error>,
        _default: Option<LabelType<TNT>>,
    ) -> Result<Self::FromRegex<DOption<DOption<TNT>>>, nfa::error::Error> {
        // NOTE: We cannot construct an atom from a set of regular
        // languages alone.  So it is appropriate to panic here, if
        // one tries to do so, for some reason.
        unimplemented!()
    }

    #[inline]
    fn remove_dead(&mut self, reserve: impl FnMut(usize) -> bool) -> Result<(), nfa::error::Error> {
        self.nfa.remove_dead(reserve)
    }

    #[inline]
    fn closure(
        &mut self,
        predicate: impl FnMut(LabelType<TNT>) -> bool,
        remove_after_p: bool,
        transform: impl FnMut(nfa::TwoEdges<LabelType<TNT>>) -> LabelType<TNT>,
        remove_predicate: impl FnMut(LabelType<TNT>) -> bool,
    ) -> Result<(), nfa::error::Error> {
        self.nfa
            .closure(predicate, remove_after_p, transform, remove_predicate)
    }
}

impl DefaultAtom {
    /// Construct an atomic language from a grammar.
    pub fn from_grammar(mut grammar: Grammar) -> Result<Self, GrammarError> {
        grammar.compute_firsts()?;

        let regexp = grammar.left_closure()?;

        let mut nfa = grammar.left_closure_to_nfa(&regexp)?;

        use std::collections::{HashMap, HashSet};

        let accumulators: Vec<usize> = {
            let mut result = Vec::with_capacity(regexp.len() + 1);
            result.push(0);

            for regex in regexp.iter() {
                // Calling `unwrap` here is safe as `result` is always
                // non-empty.
                result.push(regex.nodes_len() * 2 + result.last().unwrap());
            }

            result
        };

        let accumulators_set: HashSet<usize> = accumulators.iter().copied().collect();

        let nullables: HashSet<usize> = (0..grammar.non_num())
            .filter(|n| matches!(grammar.is_nullable(*n), Ok(true)))
            .collect();

        // Now record accepting information.

        let nfa_len = nfa.nodes_len();

        let label_is_nullable = |label: NfaLabel<DOption<TNT>>| {
            if let Some(label) = *label.get_value() {
                matches!(label, TNT::Non(n) if nullables.contains(&n))
            } else {
                true
            }
        };

        let mut accepting_vec: Vec<bool> = std::iter::repeat(false).take(nfa_len).collect();

        for nfa_start in accumulators.iter().copied().take(regexp.len()) {
            *accepting_vec.get_mut(nfa_start + 1).unwrap() = true;
        }

        // The last is always accepting.
        *accepting_vec.get_mut(nfa_len - 1).unwrap() = true;

        let mut updated = true;

        while updated {
            updated = false;

            for node in nfa.nodes() {
                // skip those that do not need to be updated
                if *accepting_vec
                    .get(node)
                    .ok_or(GrammarError::IndexOutOfBounds(node, nfa_len))?
                {
                    continue;
                }

                'label_loop: for (label, target_iter) in nfa
                    .labels_of(node)
                    .map_err(|_| GrammarError::IndexOutOfBounds(node, nfa_len))?
                {
                    if label_is_nullable(*label) {
                        for target in target_iter {
                            if *accepting_vec
                                .get(target)
                                .ok_or(GrammarError::IndexOutOfBounds(target, nfa_len))?
                            {
                                // accepting_vec[node] must have been
                                // false, as we checked above
                                *accepting_vec.get_mut(node).unwrap() = true;
                                updated = true;

                                break 'label_loop;
                            }
                        }
                    }
                }
            }
        }

        // Perform nulling and remove_epsilon at the same time.
        nfa.closure(
            label_is_nullable,
            true,
            |two_edges| grammar.transform_label_null_epsilon(two_edges),
            |label| label.get_value().is_none(),
        )?;

        nfa.remove_dead(|node| accumulators_set.contains(&node))?;

        // Now add the virtual nodes.
        let mut virtual_nodes: VirtualMap = Default::default();

        let nt_num = grammar.non_num();

        assert!(nt_num <= accumulators.len());

        /// 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: GraphError) -> GrammarError {
            match ge {
                GraphError::IndexOutOfBounds(index, bound) => {
                    GrammarError::IndexOutOfBounds(index, bound)
                }
                _ => unreachable!(),
            }
        }

        // dbg!(&accumulators);

        for nt in 0..nt_num {
            let children: std::collections::HashMap<_, _> = nfa
                // This is safe because of the above assertion.
                .labels_of(*accumulators.get(nt).unwrap())
                .map_err(index_out_of_bounds_conversion)?
                .map(|(label, target_iter)| (*label, target_iter))
                .collect();

            type TerminalsValue = (HashSet<(LabelType<TNT>, usize)>, bool);

            let mut terminals_map: HashMap<usize, TerminalsValue> = HashMap::new();

            for (label, children_iter) in children.into_iter() {
                if let Some(TNT::Ter(t)) = *label.get_value() {
                    let estimated_len = {
                        let mut result = 0;

                        for child in children_iter.clone() {
                            result += nfa.degree(child).map_err(index_out_of_bounds_conversion)?;
                        }

                        result
                    };

                    let mut accepting = false;

                    for child in children_iter {
                        accepting =
                            accepting
                                || *accepting_vec.get(child).ok_or(
                                    GrammarError::IndexOutOfBounds(child, accepting_vec.len()),
                                )?;

                        if let Some((_, old_accepting)) = terminals_map.get_mut(&t) {
                            *old_accepting = *old_accepting || accepting;
                        } else {
                            terminals_map
                                .insert(t, (HashSet::with_capacity(estimated_len), accepting));
                        }

                        for (child_label, child_children_iter) in nfa
                            .labels_of(child)
                            .map_err(index_out_of_bounds_conversion)?
                        {
                            // We checked this is safe above.
                            let (set, _) = terminals_map.get_mut(&t).unwrap();

                            set.extend(child_children_iter.map(|target| (*child_label, target)));
                        }
                    }
                }
            }

            for (t, (set, accepting)) in terminals_map.into_iter() {
                let new_index = nfa.extend(set).map_err(index_out_of_bounds_conversion)?;

                if accepting_vec.get(new_index).is_none() {
                    #[cfg(debug_assertions)]
                    assert_eq!(new_index, accepting_vec.len());

                    accepting_vec.push(accepting);
                }

                let virtual_node = VirtualNode::new(nt, t);

                virtual_nodes.insert(virtual_node, new_index);
            }
        }

        Ok(Self {
            grammar,
            nfa,
            regexp,
            virtual_nodes,
            accepting_vec,
        })
    }
}

/// A convenient getter for the map of virtual nodes.
fn query(map: &VirtualMap, nt: usize, t: usize) -> Option<usize> {
    map.get(&VirtualNode::new(nt, t)).copied()
}

impl std::ops::Deref for DefaultAtom {
    type Target = Grammar;

    fn deref(&self) -> &Self::Target {
        &self.grammar
    }
}

impl Atom for DefaultAtom {
    fn atom(&self, nt: usize, t: usize) -> Result<Option<usize>, GrammarError> {
        if nt >= self.grammar.non_num() {
            return Err(GrammarError::IndexOutOfBounds(nt, self.grammar.non_num()));
        }

        if t >= self.grammar.ter_num() {
            return Err(GrammarError::IndexOutOfBounds(t, self.grammar.ter_num()));
        }

        Ok(query(&self.virtual_nodes, nt, t))
    }

    fn empty(&self) -> usize {
        self.grammar.total() << 1
    }

    fn is_accepting(&self, node_id: usize) -> Result<bool, GrammarError> {
        self.accepting_vec
            .get(node_id)
            .copied()
            .ok_or(GrammarError::IndexOutOfBounds(
                node_id,
                self.accepting_vec.len(),
            ))
    }
}