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     new->ops = (element_t **) calloc (1, sizeof (element_t *));
  49     if (new->ops == NULL) {
  50         free (new);
  51         VERBOSE (ERROR, fprintf (stderr, "can't allocate memory\n"));
  52         return NULL;
  53     }
  54     new->func = function;
  55     new->nbops = nbops;
  56     new->prio = prio;
  57
  58     return new;
  59 }
  60
  61 /* desallocate element */
  62
  63 void delelement (element_t *root)
  64 {
  65     if ((root != NULL) && (root != ERROR_OP)) {
  66         int i;
  67         for (i = 0; i < root->nbops; i++) {
  68             if ((root->ops[i] != NULL) && (root->ops[i] != ERROR_OP)) {
  69                 delelement (root->ops[i]);
  70             }
  71         }
  72         if (root->nbops) {
  73             free (root->ops);
  74         }
  75         free (root);
  76     }
  77 }
  78
  79 /* duplicate element */
  80
  81 element_t *dupelement (element_t *root)
  82 {
  83     element_t *tmp = NULL;
  84     int i;
  85
  86     if ((root == NULL) || (root == ERROR_OP)) {
  87         return root;
  88     }
  89     tmp = newelement (root->func, root->nbops, root->prio);
  90     if (tmp == NULL) {
  91         return ERROR_OP;
  92     }
  93     tmp->value = root->value;
  94     for (i = 0; i < root->nbops; i++) {
  95         tmp->ops[i] = dupelement (root->ops[i]);
  96         if (tmp->ops[i] == ERROR_OP) {
  97             delelement (tmp);
  98             return ERROR_OP;
  99         }
 100     }
 101     return tmp;
 102 }
 103
 104 /* functions */
 105
 106 #define NB_OPERATORS 14
 107 keyword_t operators[NB_OPERATORS] = {
 108     { "+\t", Add, 2, 1, 1},
 109     { "-\t", Sub, 2, 1, 1},
 110     { "*",   Mul, 2, 1, 2},
 111     { "/",   Div, 2, 1, 2},
 112     { "%",   Mod, 2, 1, 3},
 113     { "^",   Pow, 2, 1, 4},
 114     { "==",  Equal, 2, 2, -1},
 115     { "!=",  Diff, 2, 2, -1},
 116     { ">=",  Ge, 2, 2, -1},
 117     { "<=",  Le, 2, 2, -1},
 118     { ">",   Gt, 2, 1, -1},
 119     { "<",   Lt, 2, 1, -1},
 120     { "&",   And, 2, 1, -2},
 121     { "|",   Or, 2, 1, -2}
 122 };
 123
 124 #define NB_FUNCTIONS 17
 125 keyword_t functions[NB_FUNCTIONS] = {
 126     { "sqrt", Sqr, 1, 4, 5},
 127     { "pow",  Pow, 2, 3, 5},
 128     { "cos",  Cos, 1, 3, 5},
 129     { "sin",  Sin, 1, 3, 5},
 130     { "atan", Atan, 1, 4, 5},
 131     { "exp",  Exp, 1, 3, 5},
 132     { "log",  Log, 1, 3, 5},
 133     { "sto",  Store, 2, 3, 5},
 134     { "rcl",  Recall, 1, 3, 5},
 135     { "inc",  Inc, 1, 3, 5},
 136     { "dec",  Dec, 1, 3, 5},
 137     { "disp", Disp, 0, 4, 9},
 138     { "quit", Quit, 0, 4, 9},
 139     { "help", Help, 0, 4, 9},
 140     { "!",    Not, 1, 1, 6},
 141     { "cond", Cond, 3, 4, 5},
 142     { "whl",  While, 2, 3, 5}
 143 };
 144
 145 #define NB_CONSTANTS 3
 146 keyword_t constants[NB_CONSTANTS] = {
 147     { "ans", Ans, 0, 3, 5},
 148     { "e",   E, 0, 1, 5},
 149     { "pi",  Pi, 0, 2, 5}
 150 };
 151
 152 /* subparser function */
 153
 154 element_t *subparser (element_t **proot, char **pstr, func_t func, int nbops, int prio)
 155 {
 156     element_t *new = newelement (func, nbops, prio);
 157     if (new == NULL) {
 158         return ERROR_OP;
 159     }
 160     new->ops[0] = *proot;
 161     new->ops[1] = parser (*pstr, pstr, new->prio);
 162     if ((new->ops[1] == NULL) || ((new->ops[1] != ERROR_OP) && (new->ops[1]->prio == 9))) {
 163         delelement (new->ops[1]);
 164         new->ops[1] = ERROR_OP;
 165     }
 166     if (new->ops[1] == ERROR_OP) {
 167         delelement (new);
 168         *proot = NULL;
 169         return ERROR_OP;
 170     }
 171     *proot = newelement (Val, 1, 5);
 172     if (*proot == NULL) {
 173         delelement (new);
 174         return ERROR_OP;
 175     }
 176     (*proot)->ops[0] = new;
 177
 178     return *proot;
 179 }
 180
 181 /* parser function */
 182
 183 element_t *parser (char *str, char **next, int prio)
 184 {
 185     element_t *root = NULL;
 186     int i;
 187
 188     VERBOSE (DEBUG, fprintf (stdout, "Starting parsing\n"));
 189
 190     /* main loop */
 191     while (*str != '\0') {
 192         int found = 0;
 193         element_t *new = NULL;
 194         VERBOSE (INFO, fprintf (stdout, "Processing: %s\n", str));
 195
 196         /* skip spaces and tabs */
 197
 198         if ((*str == ' ') || (*str == '\t')) {
 199             str++;
 200             continue;
 201         }
 202
 203         /* check for open brace */
 204
 205         if (*str == '{') {
 206             VERBOSE (DEBUG, fprintf (stdout, "start processing brace\n"));
 207             element_t *prog = newelement (Prog, 0, 5);
 208             if (prog == NULL) {
 209                 delelement (root);
 210                 return ERROR_OP;
 211             }
 212             if (root == NULL) {
 213                 root = prog;
 214             } else {
 215                 for (i = 0; i < root->nbops; i++) {
 216                     if (root->ops[i] == NULL) {
 217                         root->ops[i] = prog;
 218                         found = 1;
 219                     }
 220                 }
 221                 if (!found) {
 222                     delelement (prog);
 223                     delelement (root);
 224                     return ERROR_OP;
 225                 }
 226             }
 227
 228             do {
 229                 found = 0;
 230                 new = parser (str + 1, &str, 0);
 231                 if ((new == NULL) || ((new != ERROR_OP) && (new->prio == 9))) {
 232                     delelement (new);
 233                     new = ERROR_OP;
 234                 }
 235                 if ((new == NULL) || (new == ERROR_OP)) {
 236                     delelement (root);
 237                 return ERROR_OP;
 238                 }
 239                 element_t *prognew = newelement (Prog, prog->nbops + 1, 5);
 240                 for (i = 0; i < prog->nbops; i++) {
 241                     prognew->ops[i] = prog->ops[i];
 242                 }
 243                 prog->ops[prog->nbops] = new;
 244                 delelement (prog);
 245                 prog = prognew;
 246             } while (*str == ',');
 247
 248             if (*str != '}') {
 249                 delelement (root);
 250                 return ERROR_OP;
 251             }
 252             str++;
 253             VERBOSE (DEBUG, fprintf (stdout, "stop processing brace\n"));
 254             continue;
 255         }
 256
 257         /* check for open bracket */
 258
 259         if (*str == '(') {
 260             VERBOSE (DEBUG, fprintf (stdout, "start processing bracket\n"));
 261             if (root) {
 262                 do {
 263                     found = 0;
 264                     new = parser (str + 1, &str, 0);
 265                     if ((new == NULL) || ((new != ERROR_OP) && (new->prio == 9))) {
 266                         delelement (new);
 267                         new = ERROR_OP;
 268                     }
 269                     if ((new == NULL) || (new == ERROR_OP)) {
 270                         delelement (root);
 271                         return ERROR_OP;
 272                     }
 273                     for (i = 0; i < root->nbops; i++) {
 274                         if (root->ops[i] == NULL) {
 275                             root->ops[i] = new;
 276                             found = 1;
 277                             break;
 278                         }
 279                     }
 280                     if (!found) {
 281                         delelement (new);
 282                         delelement (root);
 283                         return ERROR_OP;
 284                     }
 285                 } while (*str == ',');
 286             } else {
 287                 root = newelement (Val, 1, 5);
 288                 if (root == NULL) {
 289                     return ERROR_OP;
 290                 }
 291                 new = parser (str + 1, &str, 0);
 292                 if ((new == NULL) || ((new != ERROR_OP) && (new->prio == 9))) {
 293                     delelement (new);
 294                     new = ERROR_OP;
 295                 }
 296                 if ((new == NULL) || (new == ERROR_OP) || (*str == ',')) {
 297                     delelement (new);
 298                     delelement (root);
 299                     return ERROR_OP;
 300                 }
 301                 root->ops[0] = new;
 302             }
 303             if (*str != ')') {
 304                 delelement (root);
 305                 return ERROR_OP;
 306             }
 307             str++;
 308             VERBOSE (DEBUG, fprintf (stdout, "stop processing bracket\n"));
 309             continue;
 310         }
 311
 312         /* check for closing bracket, closing brace or koma */
 313
 314         if ((*str == ')') || (*str == '}') || (*str == ',')) {
 315             if (next != NULL) {
 316                 *next = str;
 317             }
 318             return root;
 319         }
 320
 321         /* look for operators */
 322
 323         for (i = 0; i < NB_OPERATORS; i++) {
 324             keyword_t *operator = operators + i;
 325             if (codecmp (operator->keyword, str) == 0) {
 326                 VERBOSE (DEBUG, fprintf (stdout, "start processing operator\n"));
 327                 if (root) {
 328                     if ((prio) && (prio > operator->prio)) {
 329                         VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
 330                         *next = str;
 331                         return root;
 332                     }
 333                     str += operator->offset;
 334                     VERBOSE (INFO, fprintf (stdout, "Oper: %d\n", operator->func));
 335                     if (subparser (&root, &str, operator->func, operator->nbops, operator->prio) == ERROR_OP) {
 336                         delelement (root);
 337                         return ERROR_OP;
 338                     }
 339                 } else if (*str == '-') {
 340                     new = newelement (Sig, 1, 9);
 341                     if (new == NULL) {
 342                         return ERROR_OP;
 343                     }
 344                     root = new;
 345                 } else {
 346                     return ERROR_OP;
 347                 }
 348                 found = 1;
 349                 VERBOSE (DEBUG, fprintf (stdout, "stop processing operator\n"));
 350                 break;
 351             }
 352         }
 353         if (found) {
 354             continue;
 355         }
 356
 357         /* look for functions */
 358
 359         for (i = 0; i < NB_FUNCTIONS; i++) {
 360             keyword_t *function = functions + i;
 361             if (codecmp (function->keyword, str) == 0) {
 362                 VERBOSE (DEBUG, fprintf (stdout, "start processing function\n"));
 363                 if (root == NULL) {
 364                     VERBOSE (INFO, fprintf (stdout, "Func: %d\n", function->func));
 365                     new = newelement (function->func, function->nbops, function->prio);
 366                     if (new == NULL) {
 367                         return ERROR_OP;
 368                     }
 369                     root = new;
 370                 } else {
 371                     delelement (root);
 372                     return ERROR_OP;
 373                 }
 374                 str += function->offset;
 375                 found = 1;
 376                 VERBOSE (DEBUG, fprintf (stdout, "stop processing function\n"));
 377                 break;
 378             }
 379         }
 380         if (found) {
 381             continue;
 382         }
 383
 384         /* look for constant */
 385
 386         for (i = 0; i < NB_CONSTANTS; i++) {
 387             keyword_t *constant = constants + i;
 388             if (codecmp (constant->keyword, str) == 0) {
 389                 VERBOSE (DEBUG, fprintf (stdout, "start processing constant\n"));
 390                 if (root == NULL) {
 391                     VERBOSE (INFO, fprintf (stdout, "Const: %d\n", constant->func));
 392                     new = newelement (constant->func, constant->nbops, constant->prio);
 393                     if (new == NULL) {
 394                         return ERROR_OP;
 395                     }
 396                     root = new;
 397                 } else {
 398                     delelement (root);
 399                     return ERROR_OP;
 400                 }
 401                 str += constant->offset;
 402                 found = 1;
 403                 VERBOSE (DEBUG, fprintf (stdout, "stop processing constant\n"));
 404                 break;
 405             }
 406         }
 407         if (found) {
 408             continue;
 409         }
 410
 411         /* look for number */
 412
 413         if (((*str >= '0') && (*str <= '9')) ||
 414             (*str == '.') || (*str == '+') || (*str == '-')) {
 415             VERBOSE (DEBUG, fprintf (stdout, "start processing value\n"));
 416             char *pt;
 417             double value = strtod (str, &pt);
 418             VERBOSE (INFO, fprintf (stdout, "Value: %f\n", value));
 419             if (str != pt) {
 420                 if ((root == NULL) || (root->prio == 6)) {
 421                     new = newelement (Val, 1, 5);
 422                     if (new == NULL) {
 423                         return ERROR_OP;
 424                     }
 425                     new->value = value;
 426                     if (root == NULL) {
 427                         root = new;
 428                     } else {
 429                         for (i = 0; i < root->nbops; i++) {
 430                             if (root->ops[i] == NULL) {
 431                                 root->ops[i] = new;
 432                                 found = 1;
 433                                 break;
 434                             }
 435                         }
 436                         if (!found) {
 437                             delelement (new);
 438                             delelement (root);
 439                             return ERROR_OP;
 440                         }
 441                     }
 442                     str = pt;
 443                 } else if ((*str == '+') || (*str == '-')) {
 444                     if ((prio) && (prio > 1)) {
 445                         VERBOSE (DEBUG, fprintf (stdout, "stop because operator priority\n"));
 446                         *next = str;
 447                         return root;
 448                     }
 449                     if (subparser (&root, &str, Add, 2, 1) == ERROR_OP) {
 450                         delelement (root);
 451                         return ERROR_OP;
 452                     }
 453                 } else {
 454                     delelement (root);
 455                     return ERROR_OP;
 456                 }
 457                 found = 1;
 458             }
 459             VERBOSE (DEBUG, fprintf (stdout, "stop processing value\n"));
 460         }
 461
 462         /* error */
 463
 464         if (!found) {
 465             delelement (root);
 466             return ERROR_OP;
 467         }
 468
 469     }
 470
 471     if (next != NULL) {
 472         *next = str;
 473     }
 474
 475     return root;
 476 }
 477
 478 /* print element tree */
 479
 480 void print_element (element_t *root, int level)
 481 {
 482     char *func = NULL;
 483     int i;
 484
 485     if ((root == NULL) || (root == ERROR_OP)) {
 486         return;
 487     }
 488
 489     for (i = 0; i < level; i++) {
 490         fprintf (stdout, " ");
 491     }
 492
 493     switch (root->func) {
 494     case Val: func = "Value"; break;
 495     case Sig: func = "Sign"; break;
 496     case Add: func = "Addition"; break;
 497     case Sub: func = "Subtraction"; break;
 498     case Mul: func = "Multiplication"; break;
 499     case Div: func = "Division"; break;
 500     case Mod: func = "Modulo"; break;
 501     case Pow: func = "Power"; break;
 502     case Sqr: func = "Square Root"; break;
 503     case Cos: func = "Cosine"; break;
 504     case Sin: func = "Sine"; break;
 505     case Atan: func = "Arc Tangent"; break;
 506     case Log: func = "Logarithm"; break;
 507     case Exp: func = "Exponantial"; break;
 508     case Store: func = "Store"; break;
 509     case Recall: func = "Recall"; break;
 510     case Inc: func = "Increase"; break;
 511     case Dec: func = "Decrease"; break;
 512     case Disp: func = "Display"; break;
 513     case Quit: func = "Quit"; break;
 514     case Help: func = "Help"; break;
 515     case Ans: func = "Ans"; break;
 516     case Pi: func = "Pi"; break;
 517     case E: func = "E"; break;
 518     case Equal: func = "Equal"; break;
 519     case Diff: func = "Different"; break;
 520     case Ge: func = "Greater or equal"; break;
 521     case Le: func = "Lesser or equal"; break;
 522     case Gt: func = "Greater"; break;
 523     case Lt: func = "Lesser"; break;
 524     case And: func = "And"; break;
 525     case Or: func = "Or"; break;
 526     case Not: func = "Not"; break;
 527     case Cond: func = "Condition"; break;
 528     case While: func = "While"; break;
 529     case Prog: func = "Program"; break;
 530     }
 531
 532     fprintf (stdout, "Function: %s\n", func);
 533
 534     if ((root->func == Val) && (root->ops[0] == NULL)) {
 535         for (i = 0; i < level; i++) {
 536             fprintf (stdout, " ");
 537         }
 538         fprintf (stdout, "value: %f\n", root->value);
 539     } else {
 540         for (i = 0; i < root->nbops; i++) {
 541             print_element (root->ops[i], level + 1);
 542         }
 543     }
 544 }
 545
 546 /* storage functions */
 547
 548 double store (int index, double value)
 549 {
 550     if ((index > 0) && (index <= STORAGE_SIZE)) {
 551         storage[index - 1] = value;
 552     } else {
 553         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 554     }
 555     return value;
 556 }
 557
 558 double recall (int index)
 559 {
 560     if ((index > 0) && (index <= STORAGE_SIZE)) {
 561         return storage[index - 1];
 562     } else {
 563         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 564     }
 565     return 0;
 566 }
 567
 568 double increase (int index)
 569 {
 570     if ((index > 0) && (index <= STORAGE_SIZE)) {
 571         return storage[index - 1]++;
 572     } else {
 573         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 574     }
 575     return 0;
 576 }
 577
 578 double decrease (int index)
 579 {
 580     if ((index > 0) && (index <= STORAGE_SIZE)) {
 581         return storage[index - 1]--;
 582     } else {
 583         VERBOSE (WARNING, fprintf (stdout, "invalid index (%d) [1, %d]\n", index, STORAGE_SIZE));
 584     }
 585     return 0;
 586 }
 587
 588 void display (void)
 589 {
 590     int i;
 591     fprintf (stdout, "storage:");
 592     for (i = 0; i < STORAGE_SIZE; i++) {
 593         fprintf (stdout, " %g", storage[i]);
 594     }
 595     fprintf (stdout, "\n");
 596 }
 597
 598 /* While do function */
 599
 600 double while_do (element_t *cond, element_t *action)
 601 {
 602     double ret = 0;
 603     element_t *temp = NULL;
 604
 605     VERBOSE (DEBUG, fprintf (stdout, "starting while loop\n"));
 606     if (cond == NULL) {
 607         return ret;
 608     }
 609     while (1) {
 610         VERBOSE (DEBUG, fprintf (stdout, "loop...\n"));
 611
 612         temp = dupelement (cond);
 613         if (!evaluate_element (temp, 0)) {
 614             break;
 615         }
 616         if (action) {
 617             temp = dupelement (action);
 618             ret = evaluate_element (temp, 0);
 619         }
 620     }
 621
 622     VERBOSE (DEBUG, fprintf (stdout, "ending while loop\n"));
 623
 624     return ret;
 625 }
 626
 627 /* program function */
 628
 629 double program_do (element_t **prog, int nbcalls)
 630 {
 631     double ret = 0;
 632     int i;
 633     for (i = 0; i < nbcalls; i++) {
 634         ret = evaluate_element (prog[i], 0);
 635         prog[i] = NULL;
 636     }
 637     return ret;
 638 }
 639
 640 /* quit function */
 641
 642 void quit (void)
 643 {
 644     fprintf (stdout, "bye\n");
 645     exit (0);
 646 }
 647
 648 /* help message */
 649
 650 void help (void)
 651 {
 652     fprintf (stdout, "calc is a simple calculator\n\n");
 653     fprintf (stdout, "supported operators:");
 654     fprintf (stdout, " + - * / %% ^\n");
 655     fprintf (stdout, "camparison operators:");
 656     fprintf (stdout, " == != >= <= > <\n");
 657     fprintf (stdout, "logical operators:");
 658     fprintf (stdout, " & | !\n");
 659     fprintf (stdout, "supported functions:");
 660     fprintf (stdout, " pow sqrt cos sin atan log exp\n");
 661     fprintf (stdout, "storage functions:");
 662     fprintf (stdout, " sto rcl inc dec\n");
 663     fprintf (stdout, "conditional functions:");
 664     fprintf (stdout, " cond\n");
 665     fprintf (stdout, "miscellaneous functions:");
 666     fprintf (stdout, " quit help\n");
 667     fprintf (stdout, "supported constants:");
 668     fprintf (stdout, " e pi\n");
 669 }
 670
 671 /* evaluate element tree */
 672
 673 #define MASK_SUB 0x1
 674 #define MASK_DIV 0x2
 675
 676 double evaluate_element (element_t *root, char mask)
 677 {
 678     double op0 = 0, op1 = 0;
 679     char nextmask = mask;
 680
 681     if ((root == NULL) || (root == ERROR_OP)) {
 682         VERBOSE (WARNING, fprintf (stdout, "error while evaluating\n"));
 683         return 0;
 684     }
 685
 686     /* mask to manage sub operator sub and div */
 687     switch (root->func) {
 688     case Add:
 689         nextmask &= ~MASK_SUB;
 690         nextmask &= ~MASK_DIV;
 691         break;
 692     case Sub:
 693         nextmask |= MASK_SUB;
 694         nextmask &= ~MASK_DIV;
 695         break;
 696     case Mul:
 697         nextmask &= ~MASK_DIV;
 698         break;
 699     case Div:
 700         nextmask |= MASK_DIV;
 701         break;
 702     default:
 703         nextmask = mask;
 704     }
 705
 706     switch (root->func) {
 707     case Val:
 708     case Sig:
 709         op0 = (root->ops[0]) ? evaluate_element (root->ops[0], nextmask) : root->value;
 710         break;
 711     case Add:
 712     case Sub:
 713     case Mul:
 714     case Div:
 715     case Mod:
 716     case Pow:
 717     case Store:
 718     case Equal:
 719     case Diff:
 720     case Ge:
 721     case Le:
 722     case Gt:
 723     case Lt:
 724     case And:
 725     case Or:
 726         if (root->ops[1]) {
 727             op1 = evaluate_element (root->ops[1], nextmask);
 728         } else if (root->func != Store) {
 729             VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[1])\n"));
 730             return 0;
 731         }
 732         /* fallthrough */
 733     case Sqr:
 734     case Cos:
 735     case Sin:
 736     case Atan:
 737     case Log:
 738     case Exp:
 739     case Recall:
 740     case Inc:
 741     case Dec:
 742     case Not:
 743     case Cond:
 744         if (root->ops[0]) {
 745             op0 = evaluate_element (root->ops[0], 0);
 746         } else {
 747             VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[0])\n"));
 748             return 0;
 749         }
 750         break;
 751     case Disp:
 752     case Quit:
 753     case Help:
 754     case Ans:
 755     case Pi:
 756     case E:
 757     case Prog:
 758         break;
 759     case While:
 760         if (root->ops[0] == NULL) {
 761             VERBOSE (WARNING, fprintf (stdout, "error while evaluating (op[0])\n"));
 762             return 0;
 763         }
 764         break;
 765     }
 766
 767     switch (root->func) {
 768     case Val: return op0;
 769     case Sig: return -op0;
 770     case Add: return ((mask & MASK_SUB) == 0) ? op0 + op1 : op0 - op1;
 771     case Sub: return ((mask & MASK_SUB) == 0) ? op0 - op1 : op0 + op1;
 772     case Mul: return ((mask & MASK_DIV) == 0) ? op0 * op1 : op0 / op1;
 773     case Div: return ((mask & MASK_DIV) == 0) ? op0 / op1 : op0 * op1;
 774     case Mod: return fmod (op0, op1);
 775     case Pow: return pow (op0, op1);
 776     case Sqr: return sqrt (op0);
 777     case Cos: return cos (op0);
 778     case Sin: return sin (op0);
 779     case Atan: return atan (op0);
 780     case Log: return log (op0);
 781     case Exp: return exp (op0);
 782     case Store: return store ((int)op0, (op1) ? op1 : answer);
 783     case Recall: return recall ((int)op0);
 784     case Inc: return increase ((int)op0);
 785     case Dec: return decrease ((int)op0);
 786     case Disp: display (); break;
 787     case Quit: quit (); break;
 788     case Help: help (); break;
 789     case Ans: return answer;
 790     case Pi: return M_PI;
 791     case E: return M_E;
 792     case Equal: return op0 == op1;
 793     case Diff: return op0 != op1;
 794     case Ge: return op0 >= op1;
 795     case Le: return op0 <= op1;
 796     case Gt: return op0 > op1;
 797     case Lt: return op0 < op1;
 798     case And: return (op0 != 0) && (op1 != 0);
 799     case Or: return (op0 != 0) || (op1 != 0);
 800     case Not: return (op0 == 0);
 801     case Cond:
 802         if ((op0) && (root->ops[1])) {
 803             return evaluate_element (root->ops[1], 0);
 804         } else if ((!op0) && (root->ops[2])) {
 805             return evaluate_element (root->ops[2], 0);
 806         } else {
 807             return 0;
 808         }
 809     case While: return while_do (root->ops[0], root->ops[1]);
 810     case Prog: return program_do (root->ops, root->nbops);
 811     }
 812
 813     return 0;
 814 }
 815
 816 /* vim: set ts=4 sw=4 et: */