|
116
|
1 /*
|
|
|
2 expr.c
|
|
118
|
3 Copyright © 2009 William Astle
|
|
116
|
4
|
|
|
5 This file is part of LWLINK.
|
|
|
6
|
|
|
7 LWLINK is free software: you can redistribute it and/or modify it under the
|
|
|
8 terms of the GNU General Public License as published by the Free Software
|
|
|
9 Foundation, either version 3 of the License, or (at your option) any later
|
|
|
10 version.
|
|
|
11
|
|
|
12 This program is distributed in the hope that it will be useful, but WITHOUT
|
|
|
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
|
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
|
|
|
15 more details.
|
|
|
16
|
|
|
17 You should have received a copy of the GNU General Public License along with
|
|
|
18 this program. If not, see <http://www.gnu.org/licenses/>.
|
|
|
19 */
|
|
|
20
|
|
|
21 /*
|
|
|
22 This file contains the actual expression evaluator
|
|
|
23 */
|
|
|
24
|
|
|
25 #define __expr_c_seen__
|
|
|
26
|
|
|
27 #include <ctype.h>
|
|
|
28 #include <stdlib.h>
|
|
|
29 #include <string.h>
|
|
|
30
|
|
|
31 #include "expr.h"
|
|
|
32 #include "util.h"
|
|
|
33
|
|
|
34 lw_expr_stack_t *lw_expr_stack_create(void)
|
|
|
35 {
|
|
|
36 lw_expr_stack_t *s;
|
|
|
37
|
|
|
38 s = lw_malloc(sizeof(lw_expr_stack_t));
|
|
|
39 s -> head = NULL;
|
|
|
40 s -> tail = NULL;
|
|
|
41 return s;
|
|
|
42 }
|
|
|
43
|
|
|
44 void lw_expr_stack_free(lw_expr_stack_t *s)
|
|
|
45 {
|
|
|
46 while (s -> head)
|
|
|
47 {
|
|
|
48 s -> tail = s -> head;
|
|
|
49 s -> head = s -> head -> next;
|
|
|
50 lw_expr_term_free(s -> tail -> term);
|
|
|
51 lw_free(s -> tail);
|
|
|
52 }
|
|
|
53 lw_free(s);
|
|
|
54 }
|
|
|
55
|
|
|
56 void lw_expr_term_free(lw_expr_term_t *t)
|
|
|
57 {
|
|
|
58 if (t)
|
|
|
59 {
|
|
|
60 if (t -> term_type == LW_TERM_SYM)
|
|
|
61 lw_free(t -> symbol);
|
|
|
62 lw_free(t);
|
|
|
63 }
|
|
|
64 }
|
|
|
65
|
|
|
66 lw_expr_term_t *lw_expr_term_create_oper(int oper)
|
|
|
67 {
|
|
|
68 lw_expr_term_t *t;
|
|
|
69
|
|
|
70 t = lw_malloc(sizeof(lw_expr_term_t));
|
|
|
71 t -> term_type = LW_TERM_OPER;
|
|
|
72 t -> value = oper;
|
|
|
73 return t;
|
|
|
74 }
|
|
|
75
|
|
|
76 lw_expr_term_t *lw_expr_term_create_int(int val)
|
|
|
77 {
|
|
|
78 lw_expr_term_t *t;
|
|
|
79
|
|
|
80 t = lw_malloc(sizeof(lw_expr_term_t));
|
|
|
81 t -> term_type = LW_TERM_INT;
|
|
|
82 t -> value = val;
|
|
|
83 return t;
|
|
|
84 }
|
|
|
85
|
|
|
86 lw_expr_term_t *lw_expr_term_create_sym(char *sym, int symtype)
|
|
|
87 {
|
|
|
88 lw_expr_term_t *t;
|
|
|
89
|
|
|
90 t = lw_malloc(sizeof(lw_expr_term_t));
|
|
|
91 t -> term_type = LW_TERM_SYM;
|
|
|
92 t -> symbol = lw_strdup(sym);
|
|
|
93 t -> value = symtype;
|
|
|
94 return t;
|
|
|
95 }
|
|
|
96
|
|
|
97 lw_expr_term_t *lw_expr_term_dup(lw_expr_term_t *t)
|
|
|
98 {
|
|
|
99 switch (t -> term_type)
|
|
|
100 {
|
|
|
101 case LW_TERM_INT:
|
|
|
102 return lw_expr_term_create_int(t -> value);
|
|
|
103
|
|
|
104 case LW_TERM_OPER:
|
|
|
105 return lw_expr_term_create_oper(t -> value);
|
|
|
106
|
|
|
107 case LW_TERM_SYM:
|
|
|
108 return lw_expr_term_create_sym(t -> symbol, t -> value);
|
|
|
109
|
|
|
110 default:
|
|
|
111 exit(1);
|
|
|
112 }
|
|
|
113 // can't get here
|
|
|
114 }
|
|
|
115
|
|
|
116 void lw_expr_stack_push(lw_expr_stack_t *s, lw_expr_term_t *t)
|
|
|
117 {
|
|
|
118 lw_expr_stack_node_t *n;
|
|
|
119
|
|
|
120 if (!s)
|
|
|
121 {
|
|
|
122 exit(1);
|
|
|
123 }
|
|
|
124
|
|
|
125 n = lw_malloc(sizeof(lw_expr_stack_node_t));
|
|
|
126 n -> next = NULL;
|
|
|
127 n -> prev = s -> tail;
|
|
|
128 n -> term = lw_expr_term_dup(t);
|
|
|
129
|
|
|
130 if (s -> head)
|
|
|
131 {
|
|
|
132 s -> tail -> next = n;
|
|
|
133 s -> tail = n;
|
|
|
134 }
|
|
|
135 else
|
|
|
136 {
|
|
|
137 s -> head = n;
|
|
|
138 s -> tail = n;
|
|
|
139 }
|
|
|
140 }
|
|
|
141
|
|
|
142 lw_expr_term_t *lw_expr_stack_pop(lw_expr_stack_t *s)
|
|
|
143 {
|
|
|
144 lw_expr_term_t *t;
|
|
|
145 lw_expr_stack_node_t *n;
|
|
|
146
|
|
|
147 if (!(s -> tail))
|
|
|
148 return NULL;
|
|
|
149
|
|
|
150 n = s -> tail;
|
|
|
151 s -> tail = n -> prev;
|
|
|
152 if (!(n -> prev))
|
|
|
153 {
|
|
|
154 s -> head = NULL;
|
|
|
155 }
|
|
|
156
|
|
|
157 t = n -> term;
|
|
|
158 n -> term = NULL;
|
|
|
159
|
|
|
160 lw_free(n);
|
|
|
161
|
|
|
162 return t;
|
|
|
163 }
|
|
|
164
|
|
|
165 /*
|
|
|
166 take an expression stack s and scan for operations that can be completed
|
|
|
167
|
|
|
168 return -1 on error, 0 on no error
|
|
|
169
|
|
|
170 possible errors are: division by zero or unknown operator
|
|
|
171
|
|
|
172 theory of operation:
|
|
|
173
|
|
|
174 scan the stack for an operator which has two constants preceding it (binary)
|
|
|
175 or 1 constant preceding it (unary) and if found, perform the calculation
|
|
|
176 and replace the operator and its operands with the result
|
|
|
177
|
|
|
178 repeat the scan until no futher simplications are found or if there are no
|
|
|
179 further operators or only a single term remains
|
|
|
180
|
|
|
181 */
|
|
|
182 int lw_expr_reval(lw_expr_stack_t *s, lw_expr_stack_t *(*sfunc)(char *sym, int stype, void *state), void *state)
|
|
|
183 {
|
|
|
184 lw_expr_stack_node_t *n, *n2;
|
|
|
185 lw_expr_stack_t *ss;
|
|
|
186 int c;
|
|
|
187
|
|
|
188 next_iter_sym:
|
|
|
189 // resolve symbols
|
|
|
190 // symbols that do not resolve to an expression are left alone
|
|
|
191 for (c = 0, n = s -> head; n; n = n -> next)
|
|
|
192 {
|
|
|
193 if (n -> term -> term_type == LW_TERM_SYM)
|
|
|
194 {
|
|
|
195 ss = sfunc(n -> term -> symbol, n -> term -> value, state);
|
|
|
196 if (ss)
|
|
|
197 {
|
|
|
198 c++;
|
|
|
199 // splice in the result stack
|
|
|
200 if (n -> prev)
|
|
|
201 {
|
|
|
202 n -> prev -> next = ss -> head;
|
|
|
203 }
|
|
|
204 else
|
|
|
205 {
|
|
|
206 s -> head = ss -> head;
|
|
|
207 }
|
|
|
208 ss -> head -> prev = n -> prev;
|
|
|
209 ss -> tail -> next = n -> next;
|
|
|
210 if (n -> next)
|
|
|
211 {
|
|
|
212 n -> next -> prev = ss -> tail;
|
|
|
213 }
|
|
|
214 else
|
|
|
215 {
|
|
|
216 s -> tail = ss -> tail;
|
|
|
217 }
|
|
|
218 lw_expr_term_free(n -> term);
|
|
|
219 lw_free(n);
|
|
|
220 n = ss -> tail;
|
|
|
221
|
|
|
222 ss -> head = NULL;
|
|
|
223 ss -> tail = NULL;
|
|
|
224 lw_expr_stack_free(ss);
|
|
|
225 }
|
|
|
226 }
|
|
|
227 }
|
|
|
228 if (c)
|
|
|
229 goto next_iter_sym;
|
|
|
230
|
|
|
231 next_iter:
|
|
|
232 // a single term
|
|
|
233 if (s -> head == s -> tail)
|
|
|
234 return 0;
|
|
|
235
|
|
|
236 // search for an operator
|
|
|
237 for (n = s -> head; n; n = n -> next)
|
|
|
238 {
|
|
|
239 if (n -> term -> term_type == LW_TERM_OPER)
|
|
|
240 {
|
|
|
241 if (n -> term -> value == LW_OPER_NEG
|
|
|
242 || n -> term -> value == LW_OPER_COM
|
|
|
243 )
|
|
|
244 {
|
|
|
245 // unary operator
|
|
|
246 if (n -> prev && n -> prev -> term -> term_type == LW_TERM_INT)
|
|
|
247 {
|
|
|
248 // a unary operator we can resolve
|
|
|
249 // we do the op then remove the term "n" is pointing at
|
|
|
250 if (n -> term -> value == LW_OPER_NEG)
|
|
|
251 {
|
|
|
252 n -> prev -> term -> value = -(n -> prev -> term -> value);
|
|
|
253 }
|
|
|
254 else if (n -> term -> value == LW_OPER_COM)
|
|
|
255 {
|
|
|
256 n -> prev -> term -> value = ~(n -> prev -> term -> value);
|
|
|
257 }
|
|
|
258 n -> prev -> next = n -> next;
|
|
|
259 if (n -> next)
|
|
|
260 n -> next -> prev = n -> prev;
|
|
|
261 else
|
|
|
262 s -> tail = n -> prev;
|
|
|
263
|
|
|
264 lw_expr_term_free(n -> term);
|
|
|
265 lw_free(n);
|
|
|
266 break;
|
|
|
267 }
|
|
|
268 }
|
|
|
269 else
|
|
|
270 {
|
|
|
271 // binary operator
|
|
|
272 if (n -> prev && n -> prev -> prev && n -> prev -> term -> term_type == LW_TERM_INT && n -> prev -> prev -> term -> term_type == LW_TERM_INT)
|
|
|
273 {
|
|
|
274 // a binary operator we can resolve
|
|
|
275 switch (n -> term -> value)
|
|
|
276 {
|
|
|
277 case LW_OPER_PLUS:
|
|
|
278 n -> prev -> prev -> term -> value += n -> prev -> term -> value;
|
|
|
279 break;
|
|
|
280
|
|
|
281 case LW_OPER_MINUS:
|
|
|
282 n -> prev -> prev -> term -> value -= n -> prev -> term -> value;
|
|
|
283 break;
|
|
|
284
|
|
|
285 case LW_OPER_TIMES:
|
|
|
286 n -> prev -> prev -> term -> value *= n -> prev -> term -> value;
|
|
|
287 break;
|
|
|
288
|
|
|
289 case LW_OPER_DIVIDE:
|
|
|
290 if (n -> prev -> term -> value == 0)
|
|
|
291 return -1;
|
|
|
292 n -> prev -> prev -> term -> value /= n -> prev -> term -> value;
|
|
|
293 break;
|
|
|
294
|
|
|
295 case LW_OPER_MOD:
|
|
|
296 if (n -> prev -> term -> value == 0)
|
|
|
297 return -1;
|
|
|
298 n -> prev -> prev -> term -> value %= n -> prev -> term -> value;
|
|
|
299 break;
|
|
|
300
|
|
|
301 case LW_OPER_INTDIV:
|
|
|
302 if (n -> prev -> term -> value == 0)
|
|
|
303 return -1;
|
|
|
304 n -> prev -> prev -> term -> value /= n -> prev -> term -> value;
|
|
|
305 break;
|
|
|
306
|
|
|
307 case LW_OPER_BWAND:
|
|
|
308 n -> prev -> prev -> term -> value &= n -> prev -> term -> value;
|
|
|
309 break;
|
|
|
310
|
|
|
311 case LW_OPER_BWOR:
|
|
|
312 n -> prev -> prev -> term -> value |= n -> prev -> term -> value;
|
|
|
313 break;
|
|
|
314
|
|
|
315 case LW_OPER_BWXOR:
|
|
|
316 n -> prev -> prev -> term -> value ^= n -> prev -> term -> value;
|
|
|
317 break;
|
|
|
318
|
|
|
319 case LW_OPER_AND:
|
|
|
320 n -> prev -> prev -> term -> value = (n -> prev -> term -> value && n -> prev -> prev -> term -> value) ? 1 : 0;
|
|
|
321 break;
|
|
|
322
|
|
|
323 case LW_OPER_OR:
|
|
|
324 n -> prev -> prev -> term -> value = (n -> prev -> term -> value || n -> prev -> prev -> term -> value) ? 1 : 0;
|
|
|
325 break;
|
|
|
326
|
|
|
327 default:
|
|
|
328 // return error if unknown operator!
|
|
|
329 return -1;
|
|
|
330 }
|
|
|
331
|
|
|
332 // now remove the two unneeded entries from the stack
|
|
|
333 n -> prev -> prev -> next = n -> next;
|
|
|
334 if (n -> next)
|
|
|
335 n -> next -> prev = n -> prev -> prev;
|
|
|
336 else
|
|
|
337 s -> tail = n -> prev -> prev;
|
|
|
338
|
|
|
339 lw_expr_term_free(n -> term);
|
|
|
340 lw_expr_term_free(n -> prev -> term);
|
|
|
341 lw_free(n -> prev);
|
|
|
342 lw_free(n);
|
|
|
343 break;
|
|
|
344 }
|
|
|
345 }
|
|
|
346 }
|
|
|
347 }
|
|
|
348 // note for the terminally confused about dynamic memory and pointers:
|
|
|
349 // n will not be NULL even after the lw_free calls above so
|
|
|
350 // this test will still work (n will be a dangling pointer)
|
|
|
351 // (n will only be NULL if we didn't find any operators to simplify)
|
|
|
352 if (n)
|
|
|
353 goto next_iter;
|
|
|
354
|
|
|
355 return 0;
|
|
|
356 }
|
