summaryrefslogtreecommitdiff
path: root/src/lib/tokenize.rs
blob: 483536f22211fead26d215b7e3f4921c988ef8aa (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
use super::types::Type;
use super::types::FloatType;
use super::types::Number;
use super::types::Op;
use super::sexpr::SExpr;

pub type MaybeToken = (Option<Result<Token, String>>, usize);

#[derive(PartialEq, Debug)]
pub enum Token {
    LParen,
    RParen,
    Value(Type)
}

pub struct TokenStream {
    expr: String,
    index: usize,
    rules: Vec<fn(&str) -> MaybeToken>,
    on_err: String,
}

impl TokenStream {
    /// Creates a new TokenStream object with the provided string.
    pub fn new(expr: String, rules: Vec<fn(&str) -> MaybeToken>) -> TokenStream {
        TokenStream {
            expr,
            index: 0,
            rules,
            on_err: "ERROR".to_string(),
        }
    }

    pub fn default(e: &str) -> TokenStream {
        TokenStream {
            expr: e.to_string(),
            index: 0,
            rules: vec!(is_paren, is_op, is_bool, is_var, is_string, is_number),
            on_err: "ERROR".to_string(),
        }
    }

    pub fn peek(&self) -> Option<Result<Token, String>> {

        let i = self.count_whitespace();
        if self.index + i == self.expr.len() {
            return None
        }
        /*
        let (token, _) = analyze(&self.expr[self.index + i..],
                                 self.rules.as_slice(),
                                 &self.on_err);
         */
        let (token, _) = analyze2(&self.expr[self.index + i ..]);
        token
    }


    fn count_whitespace(&self) -> usize {
        let mut whitespace_count = 0;
        for x in self.expr[self.index..].chars() {
            if x.is_whitespace() {
                whitespace_count += 1;
            } else {
                break
            }
        }
        whitespace_count
    }

    fn skip_whitespace(&mut self) {
        if self.index < self.expr.len() {
            self.index += self.count_whitespace();
        }
    }
}

impl Iterator for TokenStream {
    type Item = Result<Token, String>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.index == self.expr.len() {
            return None
        }

        self.skip_whitespace();
        /*
        let (token, len) = analyze(
        &self.expr[self.index..],
        self.rules.as_ref(), &self.on_err);
         */
        let (token, len) = analyze2(&self.expr[self.index ..]);
        self.index += len;
        token
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        if self.index == self.expr.len() {
            (0, None)
        } else {
            (1, Some(self.expr.len() - self.index))
        }
    }
}

pub fn analyze(expr: &str, funs: &[fn(&str) -> MaybeToken],
               on_err: &str) -> MaybeToken {
    for &fun in funs.iter() {
        let (token, len) = fun(expr);
        if token.is_some() {
            return (token, len)
        }
    }

    (Some(Err(on_err.to_string())), 0)
}

fn analyze2(expr: &str) -> MaybeToken {
    //is_var, is_number
    let c = expr.chars().next().unwrap();
    /* Check for strings, ( and ) */
    if c == '"' {
        let close = get_string_end(expr);
        let value = Token::Value(Type::Str(expr[1 .. close + 1].to_string()));
        let expr_len = close + 2;
        return (Some(Ok(value)), expr_len)
    } else if c == '(' {
        return (Some(Ok(Token::LParen)), 1)
    } else if c == ')' {
        return (Some(Ok(Token::RParen)), 1)
    }

    let word = &expr[0 .. get_word_end(expr)];
    if word == "true" {
        (Some(Ok(Token::Value(Type::Bool(true)))), 4)
    } else if word == "false" {
        (Some(Ok(Token::Value(Type::Bool(false)))), 5)
    } else if let Ok(op) = word.parse::<Op>() {
        (Some(Ok(Token::Value(Type::Operator(op)))), word.len())
    } else if c.is_alphabetic() {
        (Some(Ok(Token::Value(Type::Symbol(word.to_string())))), word.len())
    } else if let (Some(x), len) = is_int(&word) {
        (Some(x), len)
    } else {
        is_float(&word)
    }
}

pub fn make_word(expr: &str) -> String {
    let word = expr.split(|c: char| {
        c.is_whitespace()
    }).next().unwrap();
    let termination = |c: char| { c == ')' || c == '('};
    let word_length = word.find(termination).unwrap_or_else(|| word.len());
    word[0..word_length].to_string()
}

pub fn get_word_end(expr: &str) -> usize {
    let word = expr.split(|c: char| { c.is_whitespace() }).next().unwrap();
    let termination_predicate = |c: char| { c == ')' || c == '('};
    word.find(termination_predicate).unwrap_or_else(|| word.len())
}

pub fn is_paren(expr: &str) -> MaybeToken {
    match expr.chars().next().unwrap() {
        '(' => (Some(Ok(Token::LParen)), 1),
        ')' => (Some(Ok(Token::RParen)), 1),
        _   => (None, 0)
    }
}

pub fn is_op(expr: &str) -> MaybeToken {
    let word = make_word(expr);
    match word.parse::<Op>() {
        Ok(op) => (Some(Ok(Token::Value(Type::Operator(op)))), word.len()),
        _      => (None, 0)
    }
}


pub fn is_bool(expr: &str) -> MaybeToken {
    let word = make_word(expr);
    match word.as_ref() {
        "true"  => (Some(Ok(Token::Value(Type::Bool(true)))), 4),
        "false" => (Some(Ok(Token::Value(Type::Bool(false)))), 5),
        _       => (None, 0)
    }
}

pub fn is_var(expr: &str) -> MaybeToken {
    let word = make_word(expr);
    let c = word.chars().next().unwrap();
    if c.is_alphabetic() {
        (Some(Ok(Token::Value(Type::Symbol(word.to_string())))), word.len())
    } else {
        (None, 0)
    }
}

pub fn is_string(expr: &str) -> MaybeToken {
    let c = expr.chars().next().unwrap();
    if c == '"' {
        let close = get_string_end(expr);
        let value = Token::Value(Type::Str(expr[1 .. close + 1].to_string()));
        let expr_len = close + 2;
        (Some(Ok(value)), expr_len)
    } else {
        (None, 0)
    }
}

fn get_string_end(expr: &str) -> usize {
    let mut previous = '"';
    let maybe_close = expr[1..].find(|current: char| {
        if current == '"' && previous != '\\' {
            true
        } else {
            previous = current;
            false
        }
    });

    match maybe_close {
        Some(x) => x,
        None => panic!("No string ending found!")
    }
}

pub fn is_number(expr: &str) -> MaybeToken {
    let word = make_word(expr);
    if let (Some(x), len) = is_int(&word) {
        (Some(x), len)
    } else {
        is_float(&word)
    }
}

pub fn is_int(word: &str) -> MaybeToken {
    match word.parse::<isize>() {
        Ok(x) => (Some(Ok(Token::Value(Type::Number(Number::Int(x))))), word.len()),
        _ => (None, 0)
    }
}

pub fn is_float(word: &str) -> MaybeToken {
    match word.parse::<FloatType>() {
        Ok(x) => (Some(Ok(Token::Value(Type::Number(Number::Float(x))))), word.len()),
        _ => (None, 0)
    }
}

pub fn tokenize(expr: &str) -> Result<SExpr, String> {
    let mut tokenstream = TokenStream::default(expr);
    match tokenstream.peek() {
        Some(Ok(Token::LParen)) => {
            let _ = tokenstream.next();
            descend(&mut tokenstream)
        },
        Some(Ok(Token::RParen)) => Err("Malformed expression".to_string()),
        Some(Ok(Token::Value(x))) => Ok(SExpr::Atom(x)),
        Some(Err(f)) => Err(f),
        None => Err("Empty expression".to_string())
    }
}

pub fn descend(tokenstream: &mut TokenStream) -> Result<SExpr, String> {
    let mut sexp = Vec::new();
    loop {
        let token = match tokenstream.next() {
            Some(Ok(x)) => x,
            Some(Err(f)) => return Err(f),
            None => return Err("Unexpected end of expression".to_string())
        };

        match token {
            Token::LParen => {
                let sexp_inner = match descend(tokenstream) {
                    Ok(x) => x,
                    Err(f) => return Err(f)
                };
                sexp.push(sexp_inner);
                continue;
            },
            Token::RParen => {
                break;
            },
            Token::Value(atom) => {
                sexp.push(SExpr::Atom(atom));
                continue;
            }
        }
    }

    Ok(SExpr::Sexpr(sexp))
}