parser.c

   1 #include <malloc.h>
   2 #include <math.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5
   6 #include "debug.h"
   7
   8 #include "parser.h"
   9
  10 /* global variables */
  11
  12 double answer = 0;
  13
  14 #define STORAGE_SIZE 10
  15 double storage[STORAGE_SIZE] = {0};
  16
  17 /* compare codes */
  18
  19 int codecmp (char *ref, char *str)
  20 {
  21     int sig;
  22
  23     while (*ref != '\0') {
  24         if (*ref == '\t') {
  25              sig = (*str == '.') ? -1 : ((*str >= '0') && (*str <= '9'));
  26         } else {
  27             sig = *str - *ref;
  28         }
  29         if (sig != 0) {
  30             return (sig > 0) ? 1 : -1;
  31         }
  32         str++;
  33         ref++;
  34     }
  35
  36     return 0;
  37 }
  38
  39 /* allocate new element */
  40
  41 element_t *newelement (func_t function, int nbops, int prio)
  42 {
  43     element_t *new = (element_t *) calloc (1, sizeof (element_t));
  44     if (new == NULL) {
  45         VERBOSE (ERROR, fprintf (stderr, "can't allocate memory\n"));
  46         return NULL;
  47     }
  48     if (nbops) {
  49         new->ops = (element_t **) calloc (nbops, sizeof (element_t *));
  50         if (new->ops == NULL) {
  51             free (new);
  52             VERBOSE (ERROR, fprintf (stderr, "can't allocate memory\n"));
  53             return NULL;
  54         }
  55     }
  56     new->func = function;
  57     new->nbops = nbops;
  58     new->prio = prio;
  59
  60     return new;
  61 }
  62
  63 /* desallocate element */
  64
  65 void delelement (element_t *root)
  66 {
  67     if ((root != NULL) && (root != ERROR_OP)) {
  68         int i;
  69         for (i = 0; i < root->nbops; i++) {
  70             if ((root->ops[i] != NULL) && (root->ops[i] != ERROR_OP)) {
  71                 delelement (root->ops[i]);
  72             }
  73         }
  74         if (root->nbops) {
  75             free (root->ops);
  76         }
  77         free (root);
  78     }
  79 }
  80
  81 /* duplicate element */
  82
  83 element_t *dupelement (element_t *root)
  84 {
  85     element_t *tmp = NULL;
  86     int i;
  87
  88     if ((root == NULL) || (root == ERROR_OP)) {
  89         return root;
  90     }
  91     tmp = newelement (root->func, root->nbops, root->prio);
  92     if (tmp == NULL) {
  93         return ERROR_OP;
  94     }
  95     tmp->value = root->value;
  96     for (i = 0; i < root->nbops; i++) {
  97         tmp->ops[i] = dupelement (root->ops[i]);
  98         if (tmp->ops[i] == ERROR_OP) {
  99             delelement (tmp);
 100             return ERROR_OP;
 101         }
 102     }
 103     return tmp;
 104 }
 105
 106 /* functions */
 107
 108 #define NB_OPERATORS 14
 109 keyword_t operators[NB_OPERATORS] = {
 110     { "+\t", Add, 2, 1, 1},
 111     { "-\t", Sub, 2, 1, 1},
 112     { "*",   Mul, 2, 1, 2},
 113     { "/",   Div, 2, 1, 2},
 114     { "%",   Mod, 2, 1, 3},
 115     { "^",   Pow, 2, 1, 4},
 116     { "==",  Equal, 2, 2, -1},
 117     { "!=",  Diff, 2, 2, -1},
 118     { ">=",  Ge, 2, 2, -1},
 119     { "<=",  Le, 2, 2, -1},
 120     { ">",   Gt, 2, 1, -1},
 121     { "<",   Lt, 2, 1, -1},
 122     { "&",   And, 2, 1, -2},
 123     { "|",   Or, 2, 1, -2}
 124 };
 125
 126 #define NB_FUNCTIONS 17
 127 keyword_t functions[NB_FUNCTIONS] = {
 128     { "sqrt", Sqr, 1, 4, 5},
 129     { "pow",  Pow, 2, 3, 5},
 130     { "cos",  Cos, 1, 3, 5},
 131     { "sin",  Sin, 1, 3, 5},
 132     { "atan", Atan, 1, 4, 5},
 133     { "exp",  Exp, 1, 3, 5},
 134     { "log",  Log, 1, 3, 5},
 135     { "sto",  Store, 2, 3, 5},
 136     { "rcl",  Recall, 1, 3, 5},
 137     { "inc",  Inc, 1, 3, 5},
 138     { "dec",  Dec, 1, 3, 5},
 139     { "disp", Disp, 0, 4, 9},
 140     { "quit", Quit, 0, 4, 9},
 141     { "help", Help, 0, 4, 9},
 142     { "!",    Not, 1, 1, 6},
 143     { "cond", Cond, 3, 4, 5},
 144     { "whl",  While, 2, 3, 5}
 145 };
 146
 147 #define NB_CONSTANTS 3
 148 keyword_t constants[NB_CONSTANTS] = {
 149     { "ans", Ans, 0, 3, 5},
 150     { "e",   E, 0, 1, 5},
 151     { "pi",  Pi, 0, 2, 5}
 152 };
 153
 154 /* subparser function */
 155
 156 element_t *subparser (element_t **proot, char **pstr, func_t func, int nbops, int prio)
 157 {
 158     element_t *new = newelement (func, nbops, prio);
 159     if (new == NULL) {
 160         return ERROR_OP;
 161     }
 162     new->ops[0] = *proot;
 163     new->ops[1] = parser (*pstr, pstr, new->prio);
 164     if ((new->ops[1] == NULL) || ((new->ops[1] != ERROR_OP) && (new->ops[1]->prio == 9))) {
 165         delelement (new->ops[1]);
 166         new->ops[1] = ERROR_OP;
 167     }
 168     if (new->ops[1] == ERROR_OP) {
 169         delelement (new);
 170         *proot = NULL;
 171         return ERROR_OP;
 172     }
 173     *proot = newelement (Val, 1, 5);
 174     if (*proot == NULL) {
 175         delelement (new);
 176         return ERROR_OP;
 177     }
 178     (*proot)->ops[0] = new;
 179
 180     return *proot;
 181 }
 182
 183 /* parser function */
 184
 185 element_t *parser (char *str, char **next, int prio)
 186 {
 187     element_t *root = NULL;
 188     int i;
 189
 190     VERBOSE (DEBUG, fprintf (stdout, "Starting parsing\n"));
 191
 192     /* main loop */
 193     while (*str != '\0') {
 194         int found = 0;
 195         element_t *new = NULL;
 196         VERBOSE (INFO, fprintf (stdout, "Processing: %s\n", str));
 197
 198         /* skip spaces and tabs */
 199
 200         if ((*str == ' ') || (*str == '\t')) {
 201             str++;
 202             continue;
 203         }
 204
 205         /* check for open brace */
 206
 207         if (*str == '{') {
 208             VERBOSE (DEBUG, fprintf (stdout, "start processing brace\n"));
 209             if (root != NULL) {
 210                 delelement (root);
 211                 return ERROR_OP;
 212             }
 213             element_t **prog = NULL;
 214             new = newelement (Prog, 0, 5);
 215             if (new == NULL) {
 216                 delelement (root);
 217                 return ERROR_OP;
 218             }
 219             root = new;
 220             prog = &root;
 221
 222             do {
 223                 new = parser (str + 1, &str, 0);
 224                 if ((new == NULL) || ((new != ERROR_OP) && (new->prio == 9))) {
 225                     delelement (new);
 226                     new = ERROR_OP;
 227                 }
 228                 if (new == ERROR_OP) {
 229                     delelement (root);
 230                     return ERROR_OP;
 231                 }
 232                 element_t *newprog = newelement (Prog, (*prog)->nbops + 1, 5);
 233                 for (i = 0; i < (*prog)->nbops; i++) {
 234                     newprog->ops[i] = (*prog)->ops[i];
 235                     (*prog)->ops[i] = NULL;
 236                 }
 237                 newprog->ops[(*prog)->nbops] = new;
 238                 delelement (*prog);
 239                 (*prog) = newprog;
 240             } while (*str == ',');
 241
 242             if (*str != '}') {
 243                 delelement (root);
 244                 return ERROR_OP;
 245             }
 246             str++;
 247             VERBOSE (DEBUG, fprintf (stdout, "stop processing brace\n"));
 248             continue;
 249         }
 250
 251         /* check for open bracket */
 252
 253         if (*str == '(') {
 254             VERBOSE (DEBUG, fprintf (stdout, "start processing bracket\n"));
 255             if (root) {
 256                 do {
 257                     found = 0;
 258                     new = parser (str + 1, &str, 0);
 259                     if ((new == NULL) || ((new != ERROR_OP) && (new->prio == 9))) {
 260                         delelement (new);
 261                         new = ERROR_OP;
 262                     }
 263                     if ((new == NULL) || (new == ERROR_OP)) {
 264                         delelement (root);
 265                         return ERROR_OP;
 266                     }
 267                     for (i = 0; i < root->nbops; i++) {
 268                         if (root->ops[i] == NULL) {
 269                             root->ops[i] = new;
 270                             found = 1;
 271                             break;
 272                         }
 273                     }
 274                     if (!found) {
 275                         delelement (new);
 276                         delelement (root);
 277                         return ERROR_OP;
 278                     }
 279                 } while (*str == ',');
 280             } else {
 281                 root = newelement (Val, 1, 5);
 282                 if (root == NULL) {
 283                     return ERROR_OP;
 284                 }
 285                 new = parser (str + 1, &str, 0);
 286                 if ((new == NULL) || ((new != ERROR_OP) && (new->prio == 9))) {
 287                     delelement (new);
 288                     new = ERROR_OP;
 289                 }
 290                 if ((new == NULL) || (new == ERROR_OP) || (*str == ',')) {
 291                     delelement (new);
 292                     delelement (root);
 293                     return ERROR_OP;
 294                 }
 295                 root->ops[0] = new;
 296             }
 297             if (*str != ')') {
 298                 delelement (root);
 299                 return ERROR_OP;
 300             }
 301             str++;
 302             VERBOSE (DEBUG, fprintf (stdout, "stop processing bracket\n"));
 303             continue;
 304         }
 305
 306         /* check for closing bracket, closing brace or koma */
 307
 308         if ((*str == ')') || (*str == '}') || (*str == ',')) {
 309             if (next != NULL) {
 310                 *next = str;
 311             }
 312             return root;
 313         }
 314
 315         /* look for operators */
 316
 317         for (i = 0; i < NB_OPERATORS; i++) {
 318             keyword_t *operator = operators + i;
 319             if (codecmp (operator->keyword, str) == 0) {
 320                 VERBOSE (DEBUG, fprintf (stdout, "start processing operator\n"));
 321                 if (root) {
 322                     if ((prio) && (prio > operator->prio)) {
 323                         VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
 324                         *next = str;
 325                         return root;
 326                     }
 327                     str += operator->offset;
 328                     VERBOSE (INFO, fprintf (stdout, "Oper: %d\n", operator->func));
 329                     if (subparser (&root, &str, operator->func, operator->nbops, operator->prio) == ERROR_OP) {
 330                         delelement (root);
 331                         return ERROR_OP;
 332                     }
 333                 } else if (*str == '-') {
 334                     new = newelement (Sig, 1, 9);
 335                     if (new == NULL) {
 336                         return ERROR_OP;
 337                     }
 338                     root = new;
 339                 } else {
 340                     return ERROR_OP;
 341                 }
 342                 found = 1;
 343                 VERBOSE (DEBUG, fprintf (stdout, "stop processing operator\n"));
 344                 break;
 345             }
 346         }
 347         if (found) {
 348             continue;
 349         }
 350
 351         /* look for functions */
 352
 353         for (i = 0; i < NB_FUNCTIONS; i++) {
 354             keyword_t *function = functions + i;
 355             if (codecmp (function->keyword, str) == 0) {
 356                 VERBOSE (DEBUG, fprintf (stdout, "start processing function\n"));
 357                 if (root == NULL) {
 358                     VERBOSE (INFO, fprintf (stdout, "Func: %d\n", function->func));
 359                     new = newelement (function->func, function->nbops, function->prio);
 360                     if (new == NULL) {
 361                         return ERROR_OP;
 362                     }
 363                     root = new;
 364                 } else {
 365                     delelement (root);
 366                     return ERROR_OP;
 367                 }
 368                 str += function->offset;
 369                 found = 1;
 370                 VERBOSE (DEBUG, fprintf (stdout, "stop processing function\n"));
 371                 break;
 372             }
 373         }
 374         if (found) {
 375             continue;
 376         }
 377
 378         /* look for constant */
 379
 380         for (i = 0; i < NB_CONSTANTS; i++) {
 381             keyword_t *constant = constants + i;
 382             if (codecmp (constant->keyword, str) == 0) {
 383                 VERBOSE (DEBUG, fprintf (stdout, "start processing constant\n"));
 384                 if (root == NULL) {
 385                     VERBOSE (INFO, fprintf (stdout, "Const: %d\n", constant->func));
 386                     new = newelement (constant->func, constant->nbops, constant->prio);
 387                     if (new == NULL) {
 388                         return ERROR_OP;
 389                     }
 390                     root = new;
 391                 } else {
 392                     delelement (root);
 393                     return ERROR_OP;
 394                 }
 395                 str += constant->offset;
 396                 found = 1;
 397                 VERBOSE (DEBUG, fprintf (stdout, "stop processing constant\n"));
 398                 break;
 399             }
 400         }
 401         if (found) {
 402             continue;
 403         }
 404
 405         /* look for number */
 406
 407         if (((*str >= '0') && (*str <= '9')) ||
 408             (*str == '.') || (*str == '+') || (*str == '-')) {
 409             VERBOSE (DEBUG, fprintf (stdout, "start processing value\n"));
 410             char *pt;
 411             double value = strtod (str, &pt);
 412             VERBOSE (INFO, fprintf (stdout, "Value: %f\n", value));
 413             if (str != pt) {
 414                 if ((root == NULL) || (root->prio == 6)) {
 415                     new = newelement (Val, 1, 5);
 416                     if (new == NULL) {
 417                         return ERROR_OP;
 418                     }
 419                     new->value = value;
 420                     if (root == NULL) {
 421                         root = new;
 422                     } else {
 423                         for (i = 0; i < root->nbops; i++) {
 424                             if (root->ops[i] == NULL) {
 425                                 root->ops[i] = new;
 426                                 found = 1;
 427                                 break;
 428                             }
 429                         }
 430                         if (!found) {
 431                             delelement (new);
 432                             delelement (root);
 433                             return ERROR_OP;
 434                         }
 435                     }
 436                     str = pt;
 437                 } else if ((*str == '+') || (*str == '-')) {
 438                     if ((prio) && (prio > 1)) {
 439                         VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
 440                         *next = str;
 441                         return root;
 442                     }
 443                     if (subparser (&root, &str, Add, 2, 1) == ERROR_OP) {
 444                         delelement (root);
 445                         return ERROR_OP;
 446                     }
 447                 } else {
 448                     delelement (root);
 449                     return ERROR_OP;
 450                 }
 451                 found = 1;
 452             }
 453             VERBOSE (DEBUG, fprintf (stdout, "stop processing value\n"));
 454         }
 455
 456         /* error */
 457
 458         if (!found) {
 459             delelement (root);
 460             return ERROR_OP;
 461         }
 462
 463     }
 464
 465     if (next != NULL) {
 466         *next = str;
 467     }
 468
 469     return root;
 470 }
 471
 472 /* print element tree */
 473
 474 void print_element (element_t *root, int level)
 475 {
 476     char *func = NULL;
 477     int i;
 478
 479     if ((root == NULL) || (root == ERROR_OP)) {
 480         return;
 481     }
 482
 483     for (i = 0; i < level; i++) {
 484         fprintf (stdout, " ");
 485     }
 486
 487     switch (root->func) {
 488     case Val: func = "Value"; break;
 489     case Sig: func = "Sign"; break;
 490     case Add: func = "Addition"; break;
 491     case Sub: func = "Subtraction"; break;
 492     case Mul: func = "Multiplication"; break;
 493     case Div: func = "Division"; break;
 494     case Mod: func = "Modulo"; break;
 495     case Pow: func = "Power"; break;
 496     case Sqr: func = "Square Root"; break;
 497     case Cos: func = "Cosine"; break;
 498     case Sin: func = "Sine"; break;
 499     case Atan: func = "Arc Tangent"; break;
 500     case Log: func = "Logarithm"; break;
 501     case Exp: func = "Exponantial"; break;
 502     case Store: func = "Store"; break;
 503     case Recall: func = "Recall"; break;
 504     case Inc: func = "Increase"; break;
 505     case Dec: func = "Decrease"; break;
 506     case Disp: func = "Display"; break;
 507     case Quit: func = "Quit"; break;
 508     case Help: func = "Help"; break;
 509     case Ans: func = "Ans"; break;
 510     case Pi: func = "Pi"; break;
 511     case E: func = "E"; break;
 512     case Equal: func = "Equal"; break;
 513     case Diff: func = "Different"; break;
 514     case Ge: func = "Greater or equal"; break;
 515     case Le: func = "Lesser or equal"; break;
 516     case Gt: func = "Greater"; break;
 517     case Lt: func = "Lesser"; break;
 518     case And: func = "And"; break;
 519     case Or: func = "Or"; break;
 520     case Not: func = "Not"; break;
 521     case Cond: func = "Condition"; break;
 522     case While: func = "While"; break;
 523     case Prog: func = "Program"; break;
 524     }
 525
 526     fprintf (stdout, "Function: %s\n", func);
 527
 528     if ((root->func == Val) && (root->ops[0] == NULL)) {
 529         for (i = 0; i < level; i++) {
 530             fprintf (stdout, " ");
 531         }
 532         fprintf (stdout, "value: %f\n", root->value);
 533     } else {
 534         for (i = 0; i < root->nbops; i++) {
 535             print_element (root->ops[i], level + 1);
 536         }
 537     }
 538 }
 539
 540 /* storage functions */
 541
 542 double store (int index, double value)
 543 {
 544     if ((index > 0) && (index <= STORAGE_SIZE)) {
 545         storage[index - 1] = value;
 546     } else {
 547         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 548     }
 549     return value;
 550 }
 551
 552 double recall (int index)
 553 {
 554     if ((index > 0) && (index <= STORAGE_SIZE)) {
 555         return storage[index - 1];
 556     } else {
 557         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 558     }
 559     return 0;
 560 }
 561
 562 double increase (int index)
 563 {
 564     if ((index > 0) && (index <= STORAGE_SIZE)) {
 565         return storage[index - 1]++;
 566     } else {
 567         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 568     }
 569     return 0;
 570 }
 571
 572 double decrease (int index)
 573 {
 574     if ((index > 0) && (index <= STORAGE_SIZE)) {
 575         return storage[index - 1]--;
 576     } else {
 577         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 578     }
 579     return 0;
 580 }
 581
 582 void display (void)
 583 {
 584     int i;
 585     fprintf (stdout, "storage:");
 586     for (i = 0; i < STORAGE_SIZE; i++) {
 587         fprintf (stdout, " %g", storage[i]);
 588     }
 589     fprintf (stdout, "\n");
 590 }
 591
 592 /* While do function */
 593
 594 double while_do (element_t *cond, element_t *action)
 595 {
 596     double ret = 0;
 597     element_t *temp = NULL;
 598
 599     VERBOSE (DEBUG, fprintf (stdout, "starting while loop\n"));
 600     if (cond == NULL) {
 601         return ret;
 602     }
 603     while (1) {
 604         VERBOSE (DEBUG, fprintf (stdout, "loop...\n"));
 605
 606         temp = dupelement (cond);
 607         if (!evaluate_element (temp, 0)) {
 608             break;
 609         }
 610         if (action) {
 611             temp = dupelement (action);
 612             ret = evaluate_element (temp, 0);
 613         }
 614     }
 615
 616     VERBOSE (DEBUG, fprintf (stdout, "ending while loop\n"));
 617
 618     return ret;
 619 }
 620
 621 /* program function */
 622
 623 double program_do (element_t **prog, int nbcalls)
 624 {
 625     double ret = 0;
 626     int i;
 627     for (i = 0; i < nbcalls; i++) {
 628         ret = evaluate_element (prog[i], 0);
 629         prog[i] = NULL;
 630     }
 631     return ret;
 632 }
 633
 634 /* quit function */
 635
 636 void quit (void)
 637 {
 638     fprintf (stdout, "bye\n");
 639     exit (0);
 640 }
 641
 642 /* help message */
 643
 644 void help (void)
 645 {
 646     fprintf (stdout, "calc is a simple calculator\n\n");
 647     fprintf (stdout, "supported operators:");
 648     fprintf (stdout, " + - * / %% ^\n");
 649     fprintf (stdout, "camparison operators:");
 650     fprintf (stdout, " == != >= <= > <\n");
 651     fprintf (stdout, "logical operators:");
 652     fprintf (stdout, " & | !\n");
 653     fprintf (stdout, "supported functions:");
 654     fprintf (stdout, " pow sqrt cos sin atan log exp\n");
 655     fprintf (stdout, "storage functions:");
 656     fprintf (stdout, " sto rcl inc dec\n");
 657     fprintf (stdout, "conditional functions:");
 658     fprintf (stdout, " cond\n");
 659     fprintf (stdout, "miscellaneous functions:");
 660     fprintf (stdout, " quit help\n");
 661     fprintf (stdout, "supported constants:");
 662     fprintf (stdout, " e pi\n");
 663 }
 664
 665 /* evaluate element tree */
 666
 667 #define MASK_SUB 0x1
 668 #define MASK_DIV 0x2
 669
 670 double evaluate_element (element_t *root, char mask)
 671 {
 672     double op0 = 0, op1 = 0;
 673     char nextmask = mask;
 674
 675     if ((root == NULL) || (root == ERROR_OP)) {
 676         VERBOSE (WARNING, fprintf (stdout, "error while evaluating\n"));
 677         return 0;
 678     }
 679
 680     /* mask to manage sub operator sub and div */
 681     switch (root->func) {
 682     case Add:
 683         nextmask &= ~MASK_SUB;
 684         nextmask &= ~MASK_DIV;
 685         break;
 686     case Sub:
 687         nextmask |= MASK_SUB;
 688         nextmask &= ~MASK_DIV;
 689         break;
 690     case Mul:
 691         nextmask &= ~MASK_DIV;
 692         break;
 693     case Div:
 694         nextmask |= MASK_DIV;
 695         break;
 696     default:
 697         nextmask = mask;
 698     }
 699
 700     switch (root->func) {
 701     case Val:
 702     case Sig:
 703         op0 = (root->ops[0]) ? evaluate_element (root->ops[0], nextmask) : root->value;
 704         break;
 705     case Add:
 706     case Sub:
 707     case Mul:
 708     case Div:
 709     case Mod:
 710     case Pow:
 711     case Store:
 712     case Equal:
 713     case Diff:
 714     case Ge:
 715     case Le:
 716     case Gt:
 717     case Lt:
 718     case And:
 719     case Or:
 720         if (root->ops[1]) {
 721             op1 = evaluate_element (root->ops[1], nextmask);
 722         } else if (root->func != Store) {
 723             VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[1])\n"));
 724             return 0;
 725         }
 726         /* fallthrough */
 727     case Sqr:
 728     case Cos:
 729     case Sin:
 730     case Atan:
 731     case Log:
 732     case Exp:
 733     case Recall:
 734     case Inc:
 735     case Dec:
 736     case Not:
 737     case Cond:
 738         if (root->ops[0]) {
 739             op0 = evaluate_element (root->ops[0], 0);
 740         } else {
 741             VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[0])\n"));
 742             return 0;
 743         }
 744         break;
 745     case Disp:
 746     case Quit:
 747     case Help:
 748     case Ans:
 749     case Pi:
 750     case E:
 751     case Prog:
 752         break;
 753     case While:
 754         if (root->ops[0] == NULL) {
 755             VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[0])\n"));
 756             return 0;
 757         }
 758         break;
 759     }
 760
 761     switch (root->func) {
 762     case Val: return op0;
 763     case Sig: return -op0;
 764     case Add: return ((mask & MASK_SUB) == 0) ? op0 + op1 : op0 - op1;
 765     case Sub: return ((mask & MASK_SUB) == 0) ? op0 - op1 : op0 + op1;
 766     case Mul: return ((mask & MASK_DIV) == 0) ? op0 * op1 : op0 / op1;
 767     case Div: return ((mask & MASK_DIV) == 0) ? op0 / op1 : op0 * op1;
 768     case Mod: return fmod (op0, op1);
 769     case Pow: return pow (op0, op1);
 770     case Sqr: return sqrt (op0);
 771     case Cos: return cos (op0);
 772     case Sin: return sin (op0);
 773     case Atan: return atan (op0);
 774     case Log: return log (op0);
 775     case Exp: return exp (op0);
 776     case Store: return store ((int)op0, (op1) ? op1 : answer);
 777     case Recall: return recall ((int)op0);
 778     case Inc: return increase ((int)op0);
 779     case Dec: return decrease ((int)op0);
 780     case Disp: display (); break;
 781     case Quit: quit (); break;
 782     case Help: help (); break;
 783     case Ans: return answer;
 784     case Pi: return M_PI;
 785     case E: return M_E;
 786     case Equal: return op0 == op1;
 787     case Diff: return op0 != op1;
 788     case Ge: return op0 >= op1;
 789     case Le: return op0 <= op1;
 790     case Gt: return op0 > op1;
 791     case Lt: return op0 < op1;
 792     case And: return (op0 != 0) && (op1 != 0);
 793     case Or: return (op0 != 0) || (op1 != 0);
 794     case Not: return (op0 == 0);
 795     case Cond:
 796         if ((op0) && (root->ops[1])) {
 797             return evaluate_element (root->ops[1], 0);
 798         } else if ((!op0) && (root->ops[2])) {
 799             return evaluate_element (root->ops[2], 0);
 800         } else {
 801             return 0;
 802         }
 803     case While: return while_do (root->ops[0], root->ops[1]);
 804     case Prog: return program_do (root->ops, root->nbops);
 805     }
 806
 807     return 0;
 808 }
 809
 810 /* vim: set ts=4 sw=4 et: */