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

/*******************************************************************************
 * Copyright (c) 2017 Association Cénotélie (cenotelie.fr)
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General
 * Public License along with this program.
 * If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/

//! Module for the definition of grammar symbols

use std::fmt::Display;
use std::fmt::Error;
use std::fmt::Formatter;

use super::text::TextContext;
use super::text::TextPosition;
use super::text::TextSpan;
use super::tokens::Token;

/// The possible types of symbol
#[derive(Copy, Clone, Eq, PartialEq)]
pub enum SymbolType {
    /// A terminal symbol, defined in the original grammar
    Terminal,
    /// A variable symbol, defined in the original grammar
    Variable,
    /// A virtual symbol, defined in the original grammar
    Virtual
}

/// Symbol ID for inexistant symbol
pub const SID_NOTHING: u32 = 0;
/// Symbol ID of the Epsilon terminal
pub const SID_EPSILON: u32 = 1;
/// Symbol ID of the Dollar terminal
pub const SID_DOLLAR: u32 = 2;

/// Represents a grammar symbol (terminal, variable or virtual)
#[derive(Copy, Clone, Eq, PartialEq)]
pub struct Symbol {
    /// The symbol's unique identifier
    pub id: u32,
    /// The symbol's name
    pub name: &'static str
}

/// Implementation of `Display` for `Symbol`
impl Display for Symbol {
    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
        write!(f, "{}", self.name)
    }
}

/// A trait for a parsing element
pub trait SemanticElementTrait {
    /// Gets the position in the input text of this element
    fn get_position(&self) -> Option<TextPosition>;

    /// Gets the span in the input text of this element
    fn get_span(&self) -> Option<TextSpan>;

    /// Gets the context of this element in the input
    fn get_context(&self) -> Option<TextContext>;

    /// Gets the grammar symbol associated to this element
    fn get_symbol(&self) -> Symbol;

    /// Gets the value of this element, if any
    fn get_value(&self) -> Option<String>;
}

/// Represents an element of parsing data
pub enum SemanticElement<'a> {
    /// A token, i.e. a piece of text matched by a lexer
    Token(Token<'a>),
    /// A terminal symbol, defined in the original grammar
    Terminal(Symbol),
    /// A variable symbol defined in the original grammar
    Variable(Symbol),
    /// A virtual symbol, defined in the original grammar
    Virtual(Symbol)
}

impl<'a> SemanticElementTrait for SemanticElement<'a> {
    fn get_position(&self) -> Option<TextPosition> {
        match self {
            &SemanticElement::Token(ref token) => token.get_position(),
            &SemanticElement::Terminal(ref _symbol) => None,
            &SemanticElement::Variable(ref _symbol) => None,
            &SemanticElement::Virtual(ref _symbol) => None
        }
    }

    fn get_span(&self) -> Option<TextSpan> {
        match self {
            &SemanticElement::Token(ref token) => token.get_span(),
            &SemanticElement::Terminal(ref _symbol) => None,
            &SemanticElement::Variable(ref _symbol) => None,
            &SemanticElement::Virtual(ref _symbol) => None
        }
    }

    fn get_context(&self) -> Option<TextContext> {
        match self {
            &SemanticElement::Token(ref token) => token.get_context(),
            &SemanticElement::Terminal(ref _symbol) => None,
            &SemanticElement::Variable(ref _symbol) => None,
            &SemanticElement::Virtual(ref _symbol) => None
        }
    }

    fn get_symbol(&self) -> Symbol {
        match self {
            &SemanticElement::Token(ref token) => token.get_symbol(),
            &SemanticElement::Terminal(ref symbol) => *symbol,
            &SemanticElement::Variable(ref symbol) => *symbol,
            &SemanticElement::Virtual(ref symbol) => *symbol
        }
    }

    fn get_value(&self) -> Option<String> {
        match self {
            &SemanticElement::Token(ref token) => token.get_value(),
            &SemanticElement::Terminal(ref _symbol) => None,
            &SemanticElement::Variable(ref _symbol) => None,
            &SemanticElement::Virtual(ref _symbol) => None
        }
    }
}

impl<'a> SemanticElement<'a> {
    /// Gets the type of the associated symbol
    pub fn get_symbol_type(&self) -> SymbolType {
        match self {
            &SemanticElement::Token(ref _token) => SymbolType::Terminal,
            &SemanticElement::Terminal(ref _symbol) => SymbolType::Terminal,
            &SemanticElement::Variable(ref _symbol) => SymbolType::Variable,
            &SemanticElement::Virtual(ref _symbol) => SymbolType::Virtual
        }
    }
}

/// Represents the semantic body of a rule being reduced
pub trait SemanticBody {
    /// Gets the symbol at the i-th index
    fn get_element_at(&self, index: usize) -> SemanticElement;

    /// Gets the length of this body
    fn length(&self) -> usize;
}

/// Delegate for a user-defined semantic action
pub type SemanticAction = FnMut(Symbol, &SemanticBody);