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
use crate::errors::MomoaError;
use crate::location::*;
use std::iter::Peekable;
pub(crate) fn read_keyword<T: Iterator<Item = char>>(
word: &str,
it: &mut Peekable<T>,
cursor: &Location,
) -> Result<Location, MomoaError> {
let mut len = 0;
for expected in word.chars().into_iter() {
let peeked = it.peek();
match peeked {
Some(actual) if *actual == expected => {
len += 1;
it.next();
}
Some(actual) => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedCharacter {
c: *actual,
line: new_cursor.line,
column: new_cursor.column,
});
}
None => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
}
}
Ok(cursor.advance(word.len()))
}
pub(crate) fn read_string<T: Iterator<Item = char>>(
it: &mut Peekable<T>,
cursor: &Location,
) -> Result<Location, MomoaError> {
// check starting double quote
let quote = it.peek();
match quote {
Some(&'"') => {
it.next();
}
Some(c) => {
return Err(MomoaError::UnexpectedCharacter {
c: *c,
line: cursor.line,
column: cursor.column,
});
}
_ => {
return Err(MomoaError::UnexpectedEndOfInput {
line: cursor.line,
column: cursor.column,
});
}
}
// track the size of the string so we can update the cursor
let mut len = 1;
let mut string_complete = false;
while let Some(&c) = it.peek() {
match c {
// ending double quotes
'"' => {
len += 1;
it.next();
string_complete = true;
break;
}
// escape characters
'\\' => {
len += 1;
it.next();
match it.peek() {
Some('"') | Some('\\') | Some('/') | Some('b') | Some('f') | Some('n')
| Some('r') | Some('t') => {
len += 1;
it.next();
}
Some('u') => {
len += 1;
it.next();
// next four digits must be hexadecimals
for _i in 0..4 {
match it.next() {
Some(nc) if nc.is_ascii_hexdigit() => len += 1,
Some(nc) => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedCharacter {
c: nc,
line: new_cursor.line,
column: new_cursor.column,
});
}
None => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
}
}
}
Some(c) => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedCharacter {
c: *c,
line: new_cursor.line,
column: new_cursor.column,
});
}
None => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
}
}
// any other character in the string
_ => {
len += 1;
it.next();
}
}
}
if !string_complete {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
Ok(cursor.advance(len))
}
pub(crate) fn read_number<T: Iterator<Item = char>>(
it: &mut Peekable<T>,
cursor: &Location,
) -> Result<Location, MomoaError> {
let mut len = 0;
// first character may be a -
let quote = it.peek();
if quote == Some(&'-') {
len += 1;
it.next();
}
// next character must be a digit
let first_zero;
match it.peek() {
Some(c) if c.is_numeric() => {
first_zero = c == &'0';
len += 1;
it.next();
}
Some(c) => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedCharacter {
c: *c,
line: new_cursor.line,
column: new_cursor.column,
});
}
None => {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
}
// possibly followed by more numbers
while let Some(&c) = it.peek() {
match c {
'0'..='9' => {
if first_zero {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedCharacter {
c,
line: new_cursor.line,
column: new_cursor.column,
});
}
len += 1;
it.next();
}
_ => break,
}
}
// at this point, we need to check for a dot (.)
if Some(&'.') == it.peek() {
len += 1;
it.next();
// TODO: Verify that there is at least one number
// must be followed by at least one number
if None == it.peek() {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
// dot must be followed by more numbers
while let Some(&c) = it.peek() {
match c {
'0'..='9' => {
len += 1;
it.next();
}
_ => break,
}
}
}
// and now let's check for E or e
let has_e = match it.peek() {
Some('e') | Some('E') => true,
_ => false,
};
if has_e {
// consume the E
len += 1;
it.next();
// check if there's a + or -
let has_sign = match it.peek() {
Some('-') | Some('+') => true,
_ => false,
};
if has_sign {
len += 1;
it.next();
}
// now we need at least one digit
let has_digit = match it.peek() {
Some(c) if c.is_digit(10) => true,
_ => false,
};
if !has_digit {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
len += 1;
it.next();
// continue consuming digits until there are no more
while let Some(c) = it.peek() {
match c {
c if c.is_digit(10) => {
len += 1;
it.next();
}
_ => break,
}
}
}
Ok(cursor.advance(len))
}
pub(crate) fn read_line_comment<T: Iterator<Item = char>>(
it: &mut Peekable<T>,
cursor: &Location,
) -> Result<Location, MomoaError> {
// the // was read outside of this function
let mut len = 2;
while let Some(&c) = it.peek() {
match c {
'\n' => {
break;
}
_ => {
len += 1;
it.next();
}
}
}
Ok(cursor.advance(len))
}
pub(crate) fn read_block_comment<T: Iterator<Item = char>>(
it: &mut Peekable<T>,
cursor: &Location,
) -> Result<Location, MomoaError> {
// the /* was read outside of this function
let mut len = 2;
let mut complete = false;
let mut comment_cursor = cursor.clone();
let mut last_char = '*';
while let Some(&c) = it.peek() {
/*
* Tracking across newlines is a bit tricky. Basically, the
* newline character itself is considered the last character of a
* line for our purposes. So, we need to move to the next line only
* after we have seen the newline character AND another character
* after that.
*/
if last_char == '\n' {
comment_cursor = comment_cursor.advance_and_new_line(len);
len = 1;
} else {
len += 1;
}
last_char = c;
it.next();
if c == '*' {
match it.peek() {
Some('/') => {
len += 1;
it.next();
complete = true;
break;
}
Some(_) => continue,
None => {
let new_cursor = comment_cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
}
}
}
if !complete {
let new_cursor = cursor.advance(len);
return Err(MomoaError::UnexpectedEndOfInput {
line: new_cursor.line,
column: new_cursor.column,
});
}
Ok(comment_cursor.advance(len))
}