-
Notifications
You must be signed in to change notification settings - Fork 0
/
parser.c
571 lines (468 loc) · 13.6 KB
/
parser.c
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
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
#include "parser.h"
#include "common.h"
#include "hash-table/hash_table.h"
#include "io.h"
#include "reducer.h"
#include <string.h>
#include <math.h>
static int n = 1;
tokens_t parse_token(char token) {
if (token == '(') {
return L_PAREN;
} else if (token == ')') {
return R_PAREN;
} else if (token == '@') {
return LAMBDA;
} else if (token == '.') {
return DOT;
} else if (is_variable(token)) {
return VARIABLE;
} else if (token == ' ') {
return WHITESPACE;
} else if (token == '\n') {
return NEWLINE;
} else if (token == '=') {
return EQ;
} else if (token == '"') {
return QUOTE;
} else if (token == ':') {
return COLON;
}
return ERROR;
}
void p_print_token(tokens_t token) {
switch (token) {
case L_PAREN:
printf("( ");
return;
case R_PAREN:
printf(") ");
return;
case LAMBDA:
printf("@ ");
return;
case DOT:
printf(". ");
return;
case VARIABLE:
printf("VARIABLE ");
return;
case WHITESPACE:
printf("WHITESPACE ");
return;
case NEWLINE:
printf("NEWLINE ");
return;
case EQ:
printf("= ");
return;
default:
printf("ERROR ");
return;
}
}
void p_print_astNode_type(AstNode *n) {
switch (n->type) {
case 0:
printf("AstNode Type: LAMBDA_EXPR\n");
break;
case 1:
printf("AstNode Type: APPLICATION\n");
break;
case 2:
printf("AstNode Type: VAR\n");
break;
case DEFINITION:
printf("AstNode Type: DEFINITION\n");
break;
}
}
void print_ast(AstNode *node) {
if (node == NULL) {
return;
}
switch (node->type) {
case LAMBDA_EXPR:
printf("(LAMBDA %s : %s", node->node.lambda_expr->parameter, node->node.lambda_expr->type);
print_ast(node->node.lambda_expr->body);
printf(") ");
break;
case APPLICATION:
printf("(APP ");
print_ast(node->node.application->function);
print_ast(node->node.application->argument);
printf(") ");
break;
case VAR:
printf("(VAR %s ", node->node.variable->name);
if (node->node.variable->type != NULL) {
printf(": %s", node->node.variable->type);
}
printf(")");
break;
case DEFINITION:
printf("(DEFINITION %s) ", node->node.variable->name);
break;
default:
printf("(UNKNOWN) ");
}
}
bool is_variable(char token) {
int cmp = (int)token;
if (cmp == '_') return true;
if ((cmp >= 97 && cmp <= 122) || (cmp >= 65 && cmp <= 90)) {
return true;
}
return false;
}
char peek(FILE *in) {
char c = fgetc(in);
ungetc(c, in);
return c;
}
void peek_print(FILE *in, int n) {
char buffer[n + 1];
int i;
for (i = 0; i < n; i++) {
int c = fgetc(in);
if (c == EOF) {
break;
}
buffer[i] = (char)c;
}
buffer[i] = '\0';
printf("%s", buffer);
for (i--; i >= 0; i--) {
ungetc(buffer[i], in);
}
}
void consume(tokens_t t, FILE *in, char *expected) {
char c = next(in);
tokens_t p = parse_token(c);
if (p != t) {
expect(expected, c);
}
}
AstNode *create_variable(char *name, char *type) {
AstNode *var = (AstNode *)malloc(sizeof(AstNode));
HANDLE_NULL(var);
var->type = VAR;
var->node.variable = (Variable *)malloc(sizeof(Variable));
var->node.variable->name = name;
var->node.variable->type = type;
return var;
}
AstNode *create_application(AstNode *function, AstNode *argument) {
AstNode *app = (AstNode *)malloc(sizeof(AstNode));
HANDLE_NULL(app);
app->type = APPLICATION;
app->node.application = (Application *)malloc(sizeof(Application));
app->node.application->function = function;
app->node.application->argument = argument;
return app;
}
AstNode *create_lambda(char *variable, AstNode *body, char *type) {
AstNode *lambda = (AstNode *)malloc(sizeof(AstNode));
HANDLE_NULL(lambda);
lambda->type = LAMBDA_EXPR;
lambda->node.lambda_expr =
(LambdaExpression *)malloc(sizeof(LambdaExpression));
lambda->node.lambda_expr->parameter = variable;
lambda->node.lambda_expr->body = body;
lambda->node.lambda_expr->type = type;
return lambda;
}
// Alpha conversion -> if we have two lambda expressions with same variable
// name, change one of them to create a new variable: (@x.xx)(@x.x) ->
// (@x.xx)(@y.y) or -> (@x.xx)(@x'.x')
// Beta reduction: substitution -> we have to look for scope (@x.xy)z => zy
// Eta Conversion / reduction -> Converts between @x.(f x) and f whenever x does
// not appear free in f which means @x.(f x) = f if f does not make use of x
// @x.(@y.yy)x) is equivalent to (@y.yy) because f does not make use of x.
// Just convert var to var_n
char *alpha_convert(char *old) {
int digits = (int)log10(abs(n)) + 1;
char *new = malloc(strlen(old) + digits + 2);
HANDLE_NULL(new);
char num_str[digits + 1];
strcpy(new, old);
sprintf(num_str, "_%d", n);
strcat(new, num_str);
n++;
return new;
}
bool is_used(HashTable *table, char *variable) {
return table_exists(table, variable);
}
void parse_space_chars(FILE *in) {
char c = peek(in);
while (c == ' ' || c == '\n' || c == '\t') {
next(in);
c = peek(in);
}
}
AstNode *parse_lambda(HashTable *table, FILE *in) {
char parameter;
tokens_t param;
if (parse_token(peek(in)) != VARIABLE) {
expect("A variable", parameter);
}
char *var = parse_variable(in);
char *new_var = NULL;
if (is_used(table, var)) {
if (search(table, var) != NULL) {
const char * error_msg = format("A definition with name %s already exists. Cannot use same name for lambda abstraction.\n", var);
error(error_msg, __FILE__, __LINE__, __func__);
}
new_var = alpha_convert(var);
insert(table, new_var, NULL);
} else {
insert(table, var, NULL);
}
parse_space_chars(in);
consume(COLON, in, ":");
parse_space_chars(in);
if (parse_token(peek(in)) != VARIABLE) {
error("Lambda abstractions should be typed.", __FILE__, __LINE__, __func__);
}
char *type = parse_type(table, in);
consume(DOT, in, ".");
AstNode *body = parse_expression(table, in);
if (new_var != NULL) {
replace(body, var, new_var);
print_verbose("Alpha converted %s to %s\n", var, new_var);
return create_lambda(new_var, body, type);
}
return create_lambda(var, body, type);
}
AstNode *parse_expression(HashTable *table, FILE *in) {
while (parse_token(peek(in)) == WHITESPACE || parse_token(peek(in)) == NEWLINE) {
next(in);
}
tokens_t scanned = parse_token(peek(in));
if (scanned == ERROR) {
printf("Error: %c is a valid token\n", peek(in));
exit(1);
}
if (scanned == LAMBDA) {
next(in);
return parse_lambda(table, in);
}
else if (scanned == L_PAREN) {
// advance();
next(in);
AstNode *expr = parse_expression(table, in);
print_ast(expr);
tokens_t next_token = parse_token(peek(in));
// if it is a whitespace, it is a function application
if (next_token == WHITESPACE) {
AstNode *expr_2 = parse_expression(table, in);
AstNode *application = (AstNode *)malloc(sizeof(AstNode));
application->type = APPLICATION;
application->node.application =
(Application *)malloc(sizeof(Application));
application->node.application->function = expr;
application->node.application->argument = expr_2;
consume(R_PAREN, in, ")");
return application;
}
consume(R_PAREN, in, ")");
return expr;
}
else if (scanned == VARIABLE) {
char *var_name = parse_variable(in);
if (strcmp(var_name, "def") == 0) {
parse_definition(table, in);
if (peek(in) != EOF) {
return parse_expression(table, in);
}
return NULL;
} else if (strcmp(var_name, "import") == 0) {
parse_import(table, in);
if (peek(in) != EOF) {
return parse_expression(table, in);
}
} else if (strcmp(var_name, "type") == 0) {
parse_type_definition(table, in);
if (peek(in) != EOF) {
return parse_expression(table, in);
}
}
// parse variable type
char *type = NULL;
parse_space_chars(in);
// if a variable is in our table, it means its used as a bound in lambda abstraction
// therefore should not be typed (because the lambda already type it)
// so if it does not exist, it is a constant and should be typed
if (!table_exists(table, var_name)) {
if (parse_token(peek(in)) != COLON) {
const char *error_msg = format("Constant Variable %s is not typed. Please provide a type.\n", var_name);
error(error_msg, __FILE__, __LINE__, __func__);
}
consume(COLON, in, ":");
parse_space_chars(in);
type = parse_type(table, in);
}
AstNode *variable = create_variable(var_name, type);
if (search(table, var_name) != NULL) {
variable->type = DEFINITION;
}
return variable;
}
return NULL;
}
void parse_import(HashTable *table, FILE *in) {
// in this step we already parsed the string "import"
char next_token;
tokens_t n;
consume(WHITESPACE, in, "a whitespace");
consume(QUOTE, in, "\"");
char *file_path = malloc(100 * sizeof(char));
HANDLE_NULL(file_path);
next_token = next(in);
n = parse_token(next_token);
file_path[0] = '\0';
int current_length = 0;
while (n != QUOTE) {
// parse the file path
if (current_length < 100 - 1) {
file_path[current_length] = next_token;
current_length++;
file_path[current_length] = '\0';
} else {
const char *error_msg = "File path is too long. Please make sure it is less than 100 characters.";
error(error_msg, __FILE__, __LINE__, __func__);
}
next_token = next(in);
n = parse_token(next_token);
}
if (n != QUOTE) {
expect("a closing quote", next_token);
}
FILE *imported_file = get_file(file_path, "r");
HANDLE_NULL(imported_file);
char imported_tkn;
while ((imported_tkn = peek(imported_file)) != EOF) {
tokens_t scanned = parse_token(imported_tkn);
parse_space_chars(imported_file);
if (scanned == VARIABLE) {
char *var_name = parse_variable(imported_file);
if (strcmp(var_name, "def") == 0) {
parse_definition(table, imported_file);
} else if (strcmp(var_name, "type") == 0) {
parse_type_definition(table, imported_file);
} else {
const char *error_msg = format("Expected a definition in the imported file, but got %s\n", var_name);
error(error_msg, __FILE__, __LINE__, __func__);
}
}
}
return;
}
void parse_definition(HashTable *table, FILE *in) {
// at this moment the "def" string was already parsed
char next_token;
tokens_t n;
consume(WHITESPACE, in, "a whitespace");
if (parse_token(peek(in)) != VARIABLE) {
expect("a variable", next_token);
}
char *def_name = parse_variable(in);
consume(WHITESPACE, in, "a whitespace");
consume(EQ, in, "=");
consume(WHITESPACE, in, "a whitespace");
AstNode *definition = parse_expression(table, in);
insert(table, def_name, definition);
}
bool is_uppercase(char c) {
return c >= 'A' && c <= 'Z';
}
void parse_type_definition(HashTable *types_table, FILE *in) {
// at this point we already parsed the word "type"
char next_token = next(in);
tokens_t n = parse_token(next_token);
if (n != WHITESPACE) {
expect(" ", next_token);
}
next_token = peek(in);
n = parse_token(next_token);
if (n != VARIABLE) {
expect("a type definition", next_token);
}
if (!is_uppercase(next_token)) {
error("Type names must start with an uppercase letter", __FILE__, __LINE__, __func__);
}
char *type_name = parse_variable(in);
if (table_exists(types_table, type_name)) {
const char *error_msg = format("Type %s was already defined.\n", type_name);
error(error_msg, __FILE__, __LINE__, __func__);
}
insert(types_table, type_name, NULL);
}
char *parse_type(HashTable *types_table, FILE *in) {
// here we already parsed the : symbol and the whitespace after
char *type_name = malloc(256 * sizeof(char));
int index = 0;
char token = next(in);
if (!is_uppercase(token)) {
error("Types should start with an uppercase letter.", __FILE__, __LINE__, __func__);
}
type_name[index] = token;
index++;
while (is_variable(peek(in))) {
type_name[index] = next(in);
index++;
}
if (!table_exists(types_table, type_name)) {
const char *error_msg = format("Type %s was not defined.\n", type_name);
error(error_msg, __FILE__, __LINE__, __func__);
}
return type_name;
}
char *parse_variable(FILE *in) {
char *variable_name = malloc(256 * sizeof(char));
int index = 0;
while (is_variable(peek(in))) {
variable_name[index] = next(in);
index++;
}
return variable_name;
}
void expect(char *expected, char received) {
printf("Syntax Error: Expected %s , received %c \n", expected, received);
exit(EXIT_FAILURE);
}
void free_ast(AstNode *node) {
if (node == NULL) {
return;
}
switch (node->type) {
case LAMBDA_EXPR:
if (node->node.lambda_expr != NULL) {
free(node->node.lambda_expr->parameter);
free_ast(node->node.lambda_expr->body);
free(node->node.lambda_expr);
}
break;
case APPLICATION:
if (node->node.application != NULL) {
free_ast(node->node.application->function);
free_ast(node->node.application->argument);
free(node->node.application);
}
break;
case VAR:
if (node->node.variable != NULL) {
free(node->node.variable->name);
free(node->node.variable);
}
break;
default:
break;
}
free(node);
}
// Expression ::= LambdaExpression | Application | Variable
// LambdaExpression ::= "@" Identifier "." Expression
// Application ::= "(" Expression Expression ")"
// Variable ::= Identifier