lrtable/
stategraph.rs

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
use std::{collections::hash_map::HashMap, fmt::Write, hash::Hash};

use cfgrammar::{yacc::YaccGrammar, Symbol, TIdx};
use num_traits::{AsPrimitive, PrimInt, Unsigned};

use crate::{itemset::Itemset, StIdx};

#[derive(Debug)]
pub struct StateGraph<StorageT: Eq + Hash> {
    /// A vector of `(core_states, closed_states)` tuples.
    states: Vec<(Itemset<StorageT>, Itemset<StorageT>)>,
    start_state: StIdx<StorageT>,
    /// For each state in `states`, edges is a hashmap from symbols to state offsets.
    edges: Vec<HashMap<Symbol<StorageT>, StIdx<StorageT>>>,
}

impl<StorageT: 'static + Hash + PrimInt + Unsigned> StateGraph<StorageT>
where
    usize: AsPrimitive<StorageT>,
{
    pub(crate) fn new(
        states: Vec<(Itemset<StorageT>, Itemset<StorageT>)>,
        start_state: StIdx<StorageT>,
        edges: Vec<HashMap<Symbol<StorageT>, StIdx<StorageT>>>,
    ) -> Self {
        assert!(states.len() < num_traits::cast(StorageT::max_value()).unwrap());
        StateGraph {
            states,
            start_state,
            edges,
        }
    }

    /// Return this state graph's start state.
    pub fn start_state(&self) -> StIdx<StorageT> {
        self.start_state
    }

    /// Return an iterator which produces (in order from `StorageT::zero()..self.all_states_len()`)
    /// all this grammar's valid `StIdx`s.
    pub fn iter_stidxs(&self) -> Box<dyn Iterator<Item = StIdx<StorageT>>> {
        // We can use as safely, because we know that we're only generating integers from
        // 0..self.states.len() which we've already checked fits within StIdxStorageT.
        Box::new((0..self.states.len()).map(|x| StIdx(x.as_())))
    }

    /// Return the itemset for closed state `stidx`. Panics if `stidx` doesn't exist.
    pub fn closed_state(&self, stidx: StIdx<StorageT>) -> &Itemset<StorageT> {
        let (_, closed_state) = &self.states[usize::from(stidx)];
        closed_state
    }

    /// Return an iterator over all closed states in this `StateGraph`.
    pub fn iter_closed_states<'a>(
        &'a self,
    ) -> Box<dyn Iterator<Item = &'a Itemset<StorageT>> + 'a> {
        Box::new(self.states.iter().map(|(_, x)| x))
    }

    /// Return the itemset for core state `stidx` or `None` if it doesn't exist.
    pub fn core_state(&self, stidx: StIdx<StorageT>) -> &Itemset<StorageT> {
        let (core_states, _) = &self.states[usize::from(stidx)];
        core_states
    }

    /// Return an iterator over all core states in this `StateGraph`.
    pub fn iter_core_states<'a>(&'a self) -> Box<dyn Iterator<Item = &'a Itemset<StorageT>> + 'a> {
        Box::new(self.states.iter().map(|(x, _)| x))
    }

    /// How many states does this `StateGraph` contain? NB: By definition the `StateGraph` contains
    /// the same number of core and closed states.
    pub fn all_states_len(&self) -> StIdx<StorageT> {
        // We checked in the constructor that self.states.len() can fit into StIdxStorageT
        StIdx(self.states.len().as_())
    }

    /// Return the state pointed to by `sym` from `stidx` or `None` otherwise.
    pub fn edge(&self, stidx: StIdx<StorageT>, sym: Symbol<StorageT>) -> Option<StIdx<StorageT>> {
        self.edges
            .get(usize::from(stidx))
            .and_then(|x| x.get(&sym))
            .cloned()
    }

    /// Return the edges for state `stidx`. Panics if `stidx` doesn't exist.
    pub fn edges(&self, stidx: StIdx<StorageT>) -> &HashMap<Symbol<StorageT>, StIdx<StorageT>> {
        &self.edges[usize::from(stidx)]
    }

    /// How many edges does this `StateGraph` contain?
    pub fn all_edges_len(&self) -> usize {
        self.edges.iter().fold(0, |a, x| a + x.len())
    }

    /// Pretty print this stategraph as a `String`. If `core_states` is set to true, only the core
    /// states are pretty printed; if set to false, all states (including non-core states) are
    /// pretty printed.
    pub fn pp(&self, grm: &YaccGrammar<StorageT>, core_states: bool) -> String {
        fn num_digits<StorageT: 'static + Hash + PrimInt + Unsigned>(i: StIdx<StorageT>) -> usize
        where
            usize: AsPrimitive<StorageT>,
        {
            if usize::from(i) == 0 {
                1
            } else {
                ((usize::from(i) as f64).log10() as usize) + 1
            }
        }

        fn fmt_sym<StorageT: 'static + PrimInt + Unsigned>(
            grm: &YaccGrammar<StorageT>,
            sym: Symbol<StorageT>,
        ) -> String
        where
            usize: AsPrimitive<StorageT>,
        {
            match sym {
                Symbol::Rule(ridx) => grm.rule_name_str(ridx).to_string(),
                Symbol::Token(tidx) => format!("'{}'", grm.token_name(tidx).unwrap_or("")),
            }
        }

        let mut o = String::new();
        for (stidx, (core_st, closed_st)) in self.iter_stidxs().zip(self.states.iter()) {
            if stidx != self.start_state {
                o.push('\n');
            }
            {
                let padding = num_digits(self.all_states_len()) - num_digits(stidx);
                write!(o, "{}:{}", usize::from(stidx), " ".repeat(padding)).ok();
            }

            let st = if core_states { core_st } else { closed_st };
            for (i, (&(pidx, sidx), ctx)) in st.items.iter().enumerate() {
                let padding = if i == 0 {
                    0
                } else {
                    o.push_str("\n "); // Extra space to compensate for ":" printed above
                    num_digits(self.all_states_len())
                };
                write!(
                    o,
                    "{} [{} ->",
                    " ".repeat(padding),
                    grm.rule_name_str(grm.prod_to_rule(pidx))
                )
                .ok();
                for (i_sidx, i_ssym) in grm.prod(pidx).iter().enumerate() {
                    if i_sidx == usize::from(sidx) {
                        o.push_str(" .");
                    }
                    write!(o, " {}", fmt_sym(grm, *i_ssym)).ok();
                }
                if usize::from(sidx) == grm.prod(pidx).len() {
                    o.push_str(" .");
                }
                o.push_str(", {");
                let mut seen_b = false;
                for bidx in ctx.iter_set_bits(..) {
                    if seen_b {
                        o.push_str(", ");
                    } else {
                        seen_b = true;
                    }
                    // Since ctx is exactly tokens_len bits long, the call to as_ is safe.
                    let tidx = TIdx(bidx.as_());
                    if tidx == grm.eof_token_idx() {
                        o.push_str("'$'");
                    } else {
                        write!(o, "'{}'", grm.token_name(tidx).unwrap()).ok();
                    }
                }
                o.push_str("}]");
            }
            let mut edges = self.edges(stidx).iter().collect::<Vec<_>>();
            edges.sort_by(|(_, x), (_, y)| x.cmp(y));
            for (esym, e_stidx) in edges {
                write!(
                    o,
                    "\n{}{} -> {}",
                    " ".repeat(num_digits(self.all_states_len()) + 2),
                    fmt_sym(grm, *esym),
                    usize::from(*e_stidx)
                )
                .ok();
            }
        }
        o
    }

    /// Return a pretty printed version of the core states, and all edges.
    pub fn pp_core_states(&self, grm: &YaccGrammar<StorageT>) -> String {
        self.pp(grm, true)
    }

    /// Return a pretty printed version of the closed states, and all edges.
    pub fn pp_closed_states(&self, grm: &YaccGrammar<StorageT>) -> String {
        self.pp(grm, false)
    }
}

#[cfg(test)]
use cfgrammar::SIdx;

#[cfg(test)]
pub(crate) fn state_exists<StorageT: 'static + Hash + PrimInt + Unsigned>(
    grm: &YaccGrammar<StorageT>,
    is: &Itemset<StorageT>,
    nt: &str,
    prod_off: usize,
    dot: SIdx<StorageT>,
    la: Vec<&str>,
) where
    usize: AsPrimitive<StorageT>,
{
    let ab_prod_off = grm.rule_to_prods(grm.rule_idx(nt).unwrap())[prod_off];
    let ctx = &is.items[&(ab_prod_off, dot)];
    for tidx in grm.iter_tidxs() {
        let bit = ctx[usize::from(tidx)];
        let mut found = false;
        for t in la.iter() {
            let off = if t == &"$" {
                grm.eof_token_idx()
            } else {
                grm.token_idx(t).unwrap()
            };
            if off == tidx {
                if !bit {
                    panic!("bit for token {}, dot {} is not set in production {} of {} when it should be",
                           t, usize::from(dot), prod_off, nt);
                }
                found = true;
                break;
            }
        }
        if !found && bit {
            panic!(
                "bit for token {}, dot {} is set in production {} of {} when it shouldn't be",
                grm.token_name(tidx).unwrap(),
                usize::from(dot),
                prod_off,
                nt
            );
        }
    }
}

#[cfg(test)]
mod test {
    use crate::{pager::pager_stategraph, StIdx};
    use cfgrammar::{
        yacc::{YaccGrammar, YaccKind, YaccOriginalActionKind},
        Symbol,
    };

    #[test]
    #[rustfmt::skip]
    fn test_statetable_core() {
        // Taken from p13 of https://link.springer.com/article/10.1007/s00236-010-0115-6
        let grm = YaccGrammar::new(
            YaccKind::Original(YaccOriginalActionKind::GenericParseTree),
            "
            %start A
            %%
            A: 'OPEN_BRACKET' A 'CLOSE_BRACKET'
             | 'a'
             | 'b';
          "
        ).unwrap();
        let sg = pager_stategraph(&grm);
        assert_eq!(sg.all_states_len(), StIdx(7));
        assert_eq!(sg.states.iter().fold(0, |a, (x, _)| a + x.items.len()), 7);
        assert_eq!(sg.all_edges_len(), 9);

        // This follows the (not particularly logical) ordering of state numbers in the paper.
        let s0 = StIdx(0);
        sg.edge(s0, Symbol::Rule(grm.rule_idx("A").unwrap())).unwrap(); // s1
        let s2 = sg.edge(s0, Symbol::Token(grm.token_idx("a").unwrap())).unwrap();
        let s3 = sg.edge(s0, Symbol::Token(grm.token_idx("b").unwrap())).unwrap();
        let s5 = sg.edge(s0, Symbol::Token(grm.token_idx("OPEN_BRACKET").unwrap())).unwrap();
        assert_eq!(s2, sg.edge(s5, Symbol::Token(grm.token_idx("a").unwrap())).unwrap());
        assert_eq!(s3, sg.edge(s5, Symbol::Token(grm.token_idx("b").unwrap())).unwrap());
        assert_eq!(s5, sg.edge(s5, Symbol::Token(grm.token_idx("OPEN_BRACKET").unwrap())).unwrap());
        let s4 = sg.edge(s5, Symbol::Rule(grm.rule_idx("A").unwrap())).unwrap();
        sg.edge(s4, Symbol::Token(grm.token_idx("CLOSE_BRACKET").unwrap())).unwrap(); // s6
    }
}