parser-pda 0.1.6

Example of a simple parser pushdown automaton implementation
Documentation 
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


use crate::defs::{ SegmentDelimSyms::*, SegmentTypes,
    ParserCtx, PDAStackCtx, ParsedSegment };

    
fsm!( LittleParser<ParserCtx, PDAStackCtx> [
    Idle on Start          
        => NewSentence on LeftBracket  => PlainSegment,
    
    NewSentence on RightBracket => InvalidSegment,
    NewSentence on Letter(char) 
        => PlainSegment on LeftBracket 
        => PlainSegment on RightBracket peek_cmp Bracket
        => PlainSegment on RightBracket => InvalidSegment, 

    PlainSegment on EndOfSentence peek_cmp SentenceStart => NewSentence,   
    PlainSegment on EndOfSentence peek_cmp SegmentStart => NewSentence,   
    _ on EndOfSentence => NewSentence,
    _ on EndOfInput peek_cmp SentenceStart => Idle,          
    _ on EndOfInput => Idle,
],
[
    Idle entry, NewSentence exit
]);
  

on_state_handler!( Idle entry for LittleParser {
    data.index = 0;
});
on_state_handler!( NewSentence exit for LittleParser {
    stack.push(PDAStackCtx { sym: SentenceStart, seg_start: data.index} );
});

transition_handler!( Idle on Start for LittleParser {
});

transition_handler!( NewSentence on Letter(char) for LittleParser {
});

transition_handler!( NewSentence on LeftBracket for LittleParser {
    stack.push(PDAStackCtx { sym: Bracket, seg_start: data.index } );
});

transition_handler!( NewSentence on RightBracket for LittleParser {
});

transition_handler!( PlainSegment on LeftBracket for LittleParser {
    let top = stack.last().unwrap();
    if top.sym == SegmentStart || top.sym == SentenceStart {
        data.segments.push(ParsedSegment { 
            tp: SegmentTypes::Plain, 
            seg: (top.seg_start, data.index),
            rank: stack.len(), 
        });
    }
    stack.push(PDAStackCtx { sym: Bracket, seg_start: data.index} );
});

transition_handler!(PlainSegment on RightBracket peek_cmp Bracket for LittleParser {
    let top = stack.pop().unwrap();
    data.segments.push(ParsedSegment { 
        tp: SegmentTypes::Bracketed, 
        seg: (top.seg_start + 1, data.index),
        rank: stack.len(), 
    });
});

transition_handler!(PlainSegment on RightBracket for LittleParser {
    let top = stack.last().unwrap();
    data.segments.push(ParsedSegment { 
        tp: SegmentTypes::Plain, 
        seg: (top.seg_start, data.index),
        rank: stack.len(),
    });
    stack.push(PDAStackCtx { sym: SegmentStart, seg_start: data.index } );
});

transition_handler!(PlainSegment on EndOfSentence peek_cmp SentenceStart for LittleParser {
    let top = stack.pop().unwrap();
    data.segments.push(ParsedSegment { 
        tp: SegmentTypes::Sentence, 
        seg: (top.seg_start, data.index),
        rank: stack.len(),
    });
});

transition_handler!(PlainSegment on EndOfSentence peek_cmp SegmentStart for LittleParser {
    let top = stack.pop().unwrap();
    data.segments.push(ParsedSegment { 
        tp: SegmentTypes::Plain, 
        seg: (top.seg_start, data.index),
        rank: stack.len(),
    });
});

transition_handler!(_ on EndOfSentence for LittleParser {
    Self::drain_unbalanced(data, stack);
});

transition_handler!( _ on EndOfInput peek_cmp SentenceStart for LittleParser {
    data.segments.push(ParsedSegment { 
        tp: SegmentTypes::Tail, 
        seg: (stack.pop().unwrap().seg_start, data.index),
        rank: stack.len(),
    });
});
    
transition_handler!( _ on EndOfInput for LittleParser {
    Self::drain_unbalanced(data, stack);
});

transition_handler!( NewSentence on EndOfSentence for LittleParser {
});
    
impl LittleParser {
    pub fn start(&mut self) {
        self.signal(&Start);
    }
    pub fn next(&mut self, signal: &LittleParserSignals) {
        self.signal(signal);
        self.data.index += 1;
    }
    pub fn stop(&mut self) {
        self.signal(&EndOfInput);
    }

    fn drain_unbalanced(
        data: &mut <Self as LittleParserTrait>::DataItem, 
        stack: &mut Vec<<Self as LittleParserTrait>::StackSymbolItem>,
    ) {
        while let Some(top) = stack.pop() {
            let tp = 
                if Bracket == top {  SegmentTypes::UnbalancedLeftBracket } 
                else if SegmentStart == top { SegmentTypes::UnbalancedRightSth}
                else if SentenceStart == top { SegmentTypes::InvalidSentence}
                else {
                    unimplemented!();
                };
            data.segments.push(ParsedSegment { 
                tp, 
                seg: (top.seg_start, data.index),
                rank: stack.len(),
            });
        }
    }
}