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