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io.c

/*
 *  io.c -- input/output routines
 *
 */

/*   to do for new operator stuff:
 *
 * 5.  optimize seq_to_term?
 * 8.  can protect cl when in list with parens, but output does not get parens.
 * 10. -3 should be a number, -(3) should not.  Same for unary +.
 * 11. Check arity problem?
 * 12. check set_variables?
 *
 */

#include "header.h"

#define SYM_TAB_SIZE   50
#define MAX_COMPLEX  1000  /* number of operators/terms */

/* Include the following if ' should be a a quote character (like ").
   Otter has had that behavior since the beginning.  But I am changing it
   today, on Feb 19, 2004, making ' a SYM_SYM.  To revert to the old
   behavior, include the following. */

/* #define SINGLE_QUOTE */

/* Following structure is to store data on symbol that might be special op. */

struct sequence_member {
  struct term *t;
  short  binary_type;
  short  binary_prec;
  short  unary_type;
  short  unary_prec;
};

static struct sym_ent *Sym_tab[SYM_TAB_SIZE];  /* Symbol Table */

/*************
 *
 *    int str_double(string, double_ptr) -- Translate a string to a double.
 *
 *    Return(1) iff success.
 *
 *************/

int str_double(char *s,
             double *dp)
{
  char *end;
  double d;

  if (*s != '\"')
    return(0);
  else if (*(s+1) == '\"')
    return(0);
  else {
    d = strtod(s+1, &end);
    *dp = d;
    return (*end == '\"');
  }
}  /* str_double */

/*************
 *
 *    double_str(double, str) -- translate a double to a string
 *
 *    Like sprintf, except that format is built in and string is
 *    surrouded by double quotes.
 *
 *************/

void double_str(double d,
            char *s)
{
  int i, n;

  sprintf(s, Float_format, d);

  n = strlen(s);
  for (i=n; i>0; i--)
    s[i] = s[i-1];
  s[0] = '\"';
  s[n+1] = '\"';
  s[n+2] = '\0';
      
}  /* double_str */

/*************
 *
 *    int str_int(string, ilist) -- Translate a string to an integer.
 *
 *        String has optional '+' or '-' as first character.
 *    Return(1) iff success.
 *
 *************/

int str_int(char *s,
          int *np)
{
  int i, sign, n;

  i = 0;
  sign = 1;
  if (s[0] == '+' || s[0] == '-') {
    if (s[0] == '-')
      sign = -1;
    i = 1;
  }
  if (s[i] == '\0')
    return(0);
  else {
    n = 0;
    for( ; s[i] >= '0' && s[i] <= '9'; i++)
      n = n * 10 + s[i] - '0';
    *np = n * sign;
    return(s[i] == '\0');
  }
}  /* str_int */

/*************
 *
 *    int_str(int, str) -- translate an integer to a string
 *
 *************/

void int_str(int i,
           char *s)
{
  int j, sign;

  if ((sign = i) < 0)
    i = -i;

  j = 0;
  if (i == 0)
    s[j++] = '0';
  else {
    while (i > 0) {
      s[j++] = i % 10 + '0';
      i = i / 10;
    }
  }
  if (sign < 0)
    s[j++] = '-';
  s[j] = '\0';
  reverse(s);
}  /* int_str */

/*************
 *
 *    int str_long(string, long_ptr) -- Translate a string to a long.
 *
 *        String has optional '+' or '-' as first character.
 *    Return(1) iff success.
 *
 *************/

int str_long(char *s,
           long int *np)
{
  int i, sign;
  long n;

  i = 0;
  sign = 1;
  if (s[0] == '+' || s[0] == '-') {
    if (s[0] == '-')
      sign = -1;
    i = 1;
  }
  if (s[i] == '\0')
    return(0);
  else {
    n = 0;
    for( ; s[i] >= '0' && s[i] <= '9'; i++)
      n = n * 10 + s[i] - '0';
    *np = n * sign;
    return(s[i] == '\0');
  }
}  /* str_long */

/*************
 *
 *    int bits_ulong(string, long_ptr) -- Translate a string to a long.
 *
 *    String must consist only of 0's and 1's.
 *
 *    Return(1) iff success.
 *
 *************/

int bits_ulong(char *s,
             long unsigned int *np)
{
  int i;
  unsigned long n;

  n = 0;
  for(i = 0 ; s[i] == '0' || s[i] == '1'; i++)
    n = n * 2 + s[i] - '0';
  *np = n;
  return(s[i] == '\0');
}  /* bits_ulong */

/*************
 *
 *    long_str(int, str) -- translate a long to a string
 *
 *************/

void long_str(long int i,
            char *s)
{
  int j;
  long signd;

  if ((signd = i) < 0)
    i = -i;

  j = 0;
  if (i == 0)
    s[j++] = '0';
  else {
    while (i > 0) {
      s[j++] = i % 10 + '0';
      i = i / 10;
    }
  }
  if (signd < 0)
    s[j++] = '-';
  s[j] = '\0';
  reverse(s);
}  /* long_str */

/*************
 *
 *    ulong_bits(int, str) -- translate a long to a base-2 string.
 *
 *************/

void ulong_bits(long unsigned int i,
            char *s)
{
  unsigned long j;
  int n, k;

  /* Set n to the number of places we'll use. */
  /* First ignore leading 0's, then increase if necessary. */
  for (j = i, n = 0; j > 0; j = j >> 1, n++);
  n = (n < Parms[MIN_BIT_WIDTH].val ? Parms[MIN_BIT_WIDTH].val : n);
  /* build the string */
  for (k = 0; k < n; k++)
    s[k] = '0' + ((i >> (n-(k+1))) & 1);
  s[n] = '\0';
}  /* ulong_bits */

/*************
 *
 *    cat_str(s1, s2, s3)
 *
 *************/

void cat_str(char *s1,
           char *s2,
           char *s3)
{
  int i, j;

  for (i = 0; s1[i] != '\0'; i++)
    s3[i] = s1[i];
  for (j = 0; s2[j] != '\0'; j++, i++)
    s3[i] = s2[j];
  s3[i] = '\0';
}  /* cat_str */

/*************
 *
 *     int str_ident(s, t) --  Identity of strings
 *
 *************/

int str_ident(char *s,
            char *t)
{
  for ( ; *s == *t; s++, t++)
    if (*s == '\0') return(1);
  return(0);
}  /* str_ident */

/*************
 *
 *    reverse(s) -- reverse a string
 *
 *************/

void reverse(char *s)
{
  int i, j;
  char temp;

  for (i = 0, j = strlen(s)-1; i<j; i++, j--) {
    temp = s[i];
    s[i] = s[j];
    s[j] = temp;
  }
}  /* reverse */

/*************
 *
 *    struct sym_ent *insert_sym(string, arity)
 *
 *    Insert string/arity into the symbol table and return the symbol
 *    table node.  Do not check if string/arity is already there.
 *
 *************/

struct sym_ent *insert_sym(char *s,
                     int arity)
{
  struct sym_ent *p;
  int i;

  p = get_sym_ent();
  strcpy(p->name, s);
  p->arity = arity;
  p->lex_val = (2 * Parms[NEW_SYMBOL_LEX_POSITION].val) - 1;
  p->sym_num = new_sym_num();
  i = p->sym_num % SYM_TAB_SIZE;
  p->next = Sym_tab[i];
  Sym_tab[i] = p;
  return(p);
}  /* insert_sym */

/*************
 *
 *    int str_to_sn(str, arity) -- Return a symbol number for string/arity.
 *
 *        If the given string/arity is already in the global symbol table,
 *    then return symbol number; else, create a new symbol table entry and
 *    return a new symbol number
 *
 *************/

int str_to_sn(char *str,
            int arity)
{
  struct sym_ent *p, *save;
  int i;
  long dummy;

  save = NULL;
  for (i = 0; i < SYM_TAB_SIZE; i++) {
    p = Sym_tab[i];
    while (p != NULL) {
      if (!str_ident(str, p->name))
      p = p->next;
      else if (p->arity != arity) {
      save = p;
      p = p->next;
      }
      else {
      if (p->eval_code != 0)
        /* recall that evaluable symbols are inserted in init */
        Internal_flags[DOLLAR_PRESENT] = 1;
      return(p->sym_num);
      }
    }
  }

  if (save && !save->special_op &&
      Flags[CHECK_ARITY].val &&
      Internal_flags[REALLY_CHECK_ARITY] &&
      !str_ident(str, "$Quantified") &&
      !str_ident(str, "$Hyps") &&
      !str_ident(str, "$Concs")    ) {
            
    fprintf(stderr, "%c\n\nWARNING, multiple arity: %s/%d, %s/%d.\n\n", Bell,
          save->name, save->arity, str, arity);
  }

  /* String/arity not in table, so create an entry. */

  p = insert_sym(str, arity);

  if (str[0] == '$' &&

      p->sym_num != Cons_sym_num &&  /* Lists */
      p->sym_num != Nil_sym_num &&

      p->sym_num != Ignore_sym_num &&  /* Misc */
      p->sym_num != Chr_sym_num &&
      p->sym_num != Dots_sym_num &&
      !initial_str("$Quantified", str) &&

      !initial_str("$ANS", str) &&  /* Answer literals */
      !initial_str("$Ans", str) &&
      !initial_str("$ans", str) &&

      !initial_str("$Connect", str) &&  /* mace2 connection relations */

      !str_ident(str, "$NUCLEUS") &&  /* Linked inference */
      !str_ident(str, "$BOTH") &&
      !str_ident(str, "$LINK") &&
      !str_ident(str, "$SATELLITE") &&

      !str_ident(str, "$FSUB") &&     /* Hints */
      !str_ident(str, "$BSUB") &&
      !str_ident(str, "$EQUIV") &&

      !str_ident(str, "$Concs") &&    /* Sequent i/o */
      !str_ident(str, "$Hyps") &&

      !skolem_symbol(p->sym_num) &&
      !str_long(str+1, &dummy))            /* e.g.,  weight(f($3,a),-2) */

    fprintf(stderr, "%c\n\nWARNING, unrecognized $ symbol: %s.\n\n", Bell, str);
      
  return(p->sym_num);
      
}  /* str_to_sn */

/*************
 *
 *    print_syms(file_ptr) -- Display the symbol list.
 *
 *************/

void print_syms(FILE *fp)
{
  struct sym_ent *p;
  int i;

  for (i = 0; i < SYM_TAB_SIZE; i++) {
    p = Sym_tab[i];
    while (p != NULL) {
      fprintf(fp, "%d  %s/%d, lex_val=%d\n", p->sym_num, p->name, p->arity, p->lex_val);
      p = p->next;
    }
  }
}  /* print_syms */

/*************
 *
 *    p_syms()
 *
 *************/

void p_syms(void)
{
  print_syms(stdout);
}  /* p_syms */

/*************
 *
 *    char *sn_to_str(sym_num)  --  given a symbol number, return the name
 *
 *************/

char *sn_to_str(int sym_num)
{
  struct sym_ent *p;

  p = Sym_tab[sym_num % SYM_TAB_SIZE];
  while (p != NULL && p->sym_num != sym_num)
    p = p->next;
  if (p == NULL)
    return("");
  else
    return(p->name);
}  /* sn_to_str */

/*************
 *
 *    int sn_to_arity(sym_num)  --  given a symbol number, return the arity
 *
 *************/

int sn_to_arity(int sym_num)
{
  struct sym_ent *p;

  p = Sym_tab[sym_num % SYM_TAB_SIZE];
  while (p != NULL && p->sym_num != sym_num)
    p = p->next;
  if (p == NULL)
    return(-1);
  else
    return(p->arity);
}  /* sn_to_arity */

/*************
 *
 *    int sn_to_node(sym_num)
 *
 *    Given a symbol number, return the symbol table node.
 *
 *************/

struct sym_ent *sn_to_node(int sym_num)
{
  struct sym_ent *p;

  p = Sym_tab[sym_num % SYM_TAB_SIZE];
  while (p != NULL && p->sym_num != sym_num)
    p = p->next;
  return(p);  /* possibly NULL */
}  /* sn_to_node */

/*************
 *
 *    int sn_to_ec(sym_num)
 *
 *    Given a symbol number, return the evaluation code.
 *
 *************/

int sn_to_ec(int sym_num)
{
  struct sym_ent *p;

  p = Sym_tab[sym_num % SYM_TAB_SIZE];
  while (p != NULL && p->sym_num != sym_num)
    p = p->next;
  if (p == NULL)
    return(-1);
  else
    return(p->eval_code);
}  /* sn_to_ec */

/*************
 *
 *    sym_tab_member(str, arity)
 *
 *    Similar to str_to_sn, but do not insert if not there,
 *    and return node instead of sn.
 *
 *************/

struct sym_ent *sym_tab_member(char *str,
                         int arity)
{
  struct sym_ent *p;
  int i;

  for (i = 0; i < SYM_TAB_SIZE; i++) {
    p = Sym_tab[i];
    while (p != NULL) {
      if (!str_ident(str, p->name))
      p = p->next;
      else if (p->arity != arity)
      p = p->next;
      else
      return(p);
    }
  }
  return((struct sym_ent *) NULL);

}  /* sym_tab_member */

/*************
 *
 *    int in_sym_tab(s)  --  is s in the symbol table?
 *
 *************/

int in_sym_tab(char *s)
{
  struct sym_ent *p;
  int i;

  for (i = 0; i < SYM_TAB_SIZE; i++) {
    p = Sym_tab[i];
    while (p != NULL) {
      if (str_ident(p->name, s))
      return(1);
      p = p->next;
    }
  }
  return(0);
}  /* in_sym_tab */

/*************
 *
 *    free_sym_tab() -- free all symbols in the symbol table
 *
 *************/

void free_sym_tab(void)
{
  struct sym_ent *p1, *p2;
  int i;

  for (i = 0; i < SYM_TAB_SIZE; i++) {
    p1 = Sym_tab[i];
    while (p1 != NULL) {
      p2 = p1;
      p1 = p1->next;
      free_sym_ent(p2);
    }
    Sym_tab[i] = NULL;
  }
}  /* free_sym_tab */

/*************
 *
 *    int is_symbol(t, str, arity)
 *
 *    Does t have leading function symbol str with arity?
 *
 *************/

int is_symbol(struct term *t,
            char *str,
            int arity)
{
  return((t->type == COMPLEX || t->type == NAME) &&
       sn_to_arity(t->sym_num) == arity &&
       str_ident(sn_to_str(t->sym_num), str));
}  /* is_symbol */

/*************
 *
 *    mark_as_skolem(sym_num)
 *
 *************/

void mark_as_skolem(int sym_num)
{
  struct sym_ent *se;

  se = sn_to_node(sym_num);

  if (!se) {
    char s[500];
    sprintf(s, "mark_as_skolem, no symbol for %d.", sym_num);
    abend(s);
  }
  else
    se->skolem = 1;
}  /* mark_as_skolem */

/*************
 *
 *    int is_skolem(sym_num)
 *
 *************/

int is_skolem(int sym_num)
{
  struct sym_ent *se;

  se = sn_to_node(sym_num);

  if (!se) {
    char s[500];
    sprintf(s, "is_skolem, no symbol for %d.", sym_num);
    abend(s);
    return(0);  /* to quiet lint */
  }
  else
    return(se->skolem);
}  /* is_skolem */

/*************
 *
 *     int initial_str(s, t)  --  Is s an initial substring of t?
 *
 *************/

int initial_str(char *s,
            char *t)
{
  for ( ; *s == *t; s++, t++)
    if (*s == '\0') return(1);
  return(*s == '\0');
}  /* initial_str */

/*************
 *
 *    int set_vars(term)
 *
 *        Decide which of the names are really variables, and make
 *    into variables.  (This routine is used only on input terms.)
 *    Preserve the user's variable names by keeping the pointer into
 *    the symbol list.
 *
 *    If too many variables, return(0); elase return(1).
 *
 *************/

int set_vars(struct term *t)
{
  char *varnames[MAX_VARS];
  int i;

  for (i=0; i<MAX_VARS; i++)
    varnames[i] = NULL;

  return(set_vars_term(t, varnames));
}  /* set_vars */

/*************
 *
 *     int set_vars_term(term, varnames)
 *
 *************/

int set_vars_term(struct term *t,
              char **varnames)
{
  struct rel *r;
  int i, rc;

  if (t->type == COMPLEX) {
    r = t->farg;
    rc = 1;
    while (rc && r != NULL) {
      rc = set_vars_term(r->argval, varnames);
      r = r->narg;
    }
    return(rc);
  }
  else if (var_name(sn_to_str(t->sym_num)) == 0)
    return(1);
  else {
    i = 0;
    t->type = VARIABLE;
    while (i < MAX_VARS && varnames[i] != NULL &&
         varnames[i] != sn_to_str(t->sym_num))
      i++;
    if (i == MAX_VARS)
      return(0);
    else {
      if (varnames[i] == NULL)
      varnames[i] = sn_to_str(t->sym_num);
      t->varnum = i;
      return(1);
      /* t->sym_num = 0;  include this to destroy input variable names */
    }
  }
}  /* set_vars_term */

/*************
 *
 *    int var_name(string) -- Decide if a string represents a variable.
 *
 *        return("string is a variable")
 *
 *************/

int var_name(char *s)
{
  if (Flags[PROLOG_STYLE_VARIABLES].val)
    return((*s >= 'A' && *s <= 'Z') || *s == '_');
  else
    return(*s >= 'u' && *s <= 'z');
}  /* var_name */

/*************
 *
 *    struct term *read_list(file_ptr, errors_ptr, integrate)
 *
 *    Read and return a list of terms.
 *
 *    The list must be terminated either with the term `end_of_list.'
 *    or with an actual EOF.
 *    Set errors_ptr to point to the number of errors found.
 *
 *************/

struct term_ptr *read_list(FILE *fp,
                     int *ep,
                     int integrate)
{
  struct term_ptr *p1, *p2, *p3;
  struct term *t;
  int rc;

  *ep = 0;
  p3 = NULL;
  p2 = NULL;
  t = read_term(fp, &rc);
  while (rc == 0) {
    (*ep)++;
    t = read_term(fp, &rc);
  }

  /* keep going until t == NULL || t is end marker */

  while (t != NULL && (t->type != NAME ||
                   str_ident(sn_to_str(t->sym_num), "end_of_list") == 0)) {
    if (integrate)
      t = integrate_term(t);
    p1 = get_term_ptr();
    p1->term = t;
    if (p2 == NULL)
      p3 = p1;
    else
      p2->next = p1;
    p2 = p1;
    t = read_term(fp, &rc);
    while (rc == 0) {
      (*ep)++;
      t = read_term(fp, &rc);
    }
  }
  if (t == NULL)
    return(p3);
  else {
    zap_term(t);
    return(p3);
  }
}  /* read_list */

/*************
 *
 *    print_list(file_ptr, term_ptr) -- Print a list of terms.
 *
 *        The list is printed with periods after each term, and
 *    the list is terminated with `end_of_list.' so that it can
 *    be read with read_list.
 *
 *************/

void print_list(FILE *fp,
            struct term_ptr *p)
{
  while (p != NULL) {
    print_term(fp, p->term); fprintf(fp, ".\n");
    p = p->next;
  }
  fprintf(fp, "end_of_list.\n");
}  /* print_list */

/*************
 *
 *    bird_print(fp, t)
 *
 *************/

void bird_print(FILE *fp,
            struct term *t)
{
  struct rel *r;

  if (t == NULL)
    fprintf(fp, "(nil)");
  else if (!is_symbol(t, "a", 2)) {
    /* t is not of the form a(_,_), so print in prefix */
    if (t->type == NAME)            /* name */
      fprintf(fp, "%s", sn_to_str(t->sym_num));
    else if (t->type == VARIABLE)               /* variable */
      print_variable(fp, t);
    else {  /* complex */
      fprintf(fp, "%s", sn_to_str(t->sym_num));
      fprintf(fp, "(");
      r = t->farg;
      while(r != NULL) {
      bird_print(fp, r->argval);
      r = r->narg;
      if(r != NULL)
        fprintf(fp, ",");
      }
      fprintf(fp, ")");
    }
  }
  else {  /* t has form a(_,_), so print in bird notation */
    if (is_symbol(t->farg->narg->argval, "a", 2)) {
      bird_print(fp, t->farg->argval);
      fprintf(fp, " (");
      bird_print(fp, t->farg->narg->argval);
      fprintf(fp, ")");
    }
    else {
      bird_print(fp, t->farg->argval);
      fprintf(fp, " ");
      bird_print(fp, t->farg->narg->argval);
    }
  }
}  /* bird_print */

/****************************************

write_term outputs a term in readable format (w.r.t. infix, prefix,
and postfix operators) and without extra parentheses.  It it much
complicated by one feature: deciding where to omit space around
the special operators.  For example, just as we can input a+b+c
instead of a + b + c, we wish to output without spaces were possible.
(I'm sorry the code is so complicated---I couldn't see a simpler way
of doing it.)

There are 2 types of constant/operator/functor:

    NAME_SYM: string of alphanumerics, $, and _.  Also quoted string.
    SYM_SYM:  string of *+-/\^<>=`~:?@&!;# and sometimes | (if not in list)

For completeness, the other characters are
    ,()[]{} and sometimes | (if in list)   puctuation for building terms
    .                                      end of input term
    %                                      start of comment
    "'                                     for quoted strings

For this problem, tokens are of 4 types:
    NAME_SYM
    SYM_SYM
    OPEN_PAREN  '('
    OTHER_PUNC   other punctuation (including space)

Special ops that are NAME_SYMs are always surrounded by spaces.

Here are the space rules for SYM_SYM special ops:

    infix
        omit space before if preceding token is NAME_SYM or OTHER_PUNC
        omit space after if next token is is NAME_SYM or OTHER_PUNC
              (note that space is included if next is '(')

    prefix
        omit space before if preceding token is OTHER_PUNC
        omit space after if next token is is NAME_SYM or OTHER_PUNC

    postfix
        omit space before if preceding token is NAME_SYM or OTHER_PUNC
        always include space after (could omit if next token is OTHER_PUNC,
            but current mechanism won't handle that, and it's not
            that important)

*****************************************/

/* Token types */

#define OPEN_PAREN  1
#define OTHER_PUNC  2
#define NAME_SYM    6
#define SYM_SYM     7

/*************
 *
 *    int next_token_type(t, n)
 *
 *    Find the next token type that would be output for t.
 *    n is precedence parameter as in write term.
 *
 *************/

static int next_token_type(struct term *t,
                     int n)
{
  struct sym_ent *s;
  int na1;
  char *str;

  str = sn_to_str(t->sym_num);
  if (t->type == NAME) {
    if (str_ident(str, "$nil"))
      return(OTHER_PUNC);
    else
      return(name_sym(str) ? NAME_SYM : SYM_SYM);
  }
  else if (t->type == VARIABLE) {
    if (t->sym_num == 0)
      return(NAME_SYM);
    else
      return(name_sym(str) ? NAME_SYM : SYM_SYM);
  }
  else {  /* complex */
    if (t->sym_num == str_to_sn("$cons", 2))
      return(OTHER_PUNC);
    else if (str_ident(sn_to_str(t->sym_num), "$Quantified")) {
      /* parens if parent is special op */
      if (n < 1000)
      return(OPEN_PAREN);
      else
      return(next_token_type(t->farg->argval, 0));
    }
    else {
      s = sn_to_node(t->sym_num);
      if (s->special_op && s->arity == 2) {
      na1 = s->op_prec;
      if (s->op_type == XFX || s->op_type == XFY)
        na1--;
      if (s->op_prec > n)
        return(OPEN_PAREN);
      else
        return(next_token_type(t->farg->argval, na1));
      }
      else if (s->special_op && s->arity == 1) {
      na1 = s->op_prec;
      if (s->op_type == FX || s->op_type == XF)
        na1--;

      if (s->op_prec > n)
        return(OPEN_PAREN);
      if (s->op_type == FX || s->op_type == FY)
        return(name_sym(str) ? NAME_SYM : SYM_SYM);
      else
        return(next_token_type(t->farg->argval, na1));
      }
      else
      return(name_sym(str) ? NAME_SYM : SYM_SYM);
    }
  }
}  /* next_token_type */

/*************
 *
 *    write_term(file_ptr, term, n, prev) -- print in readable form.
 *
 *************/

void write_term(FILE *fp,
            struct term *t,
            int n,
            int *prev)
{
  struct rel *r;
  struct term *t1;
  struct sym_ent *s;
  int na1, na2, next;
  char *str, *s1, *s2;

  if (t == NULL) {
    fprintf(fp, "<write_term gets NULL pointer>");
    return;
  }

  if (t->type == NAME) {
    str = sn_to_str(t->sym_num);
    if (str_ident(str, "$nil"))
      { fprintf(fp, "[]"); *prev = OTHER_PUNC;}
    else {
      fprintf(fp, "%s", str);
      *prev = (name_sym(str) ? NAME_SYM : SYM_SYM);
    }
  }

  else if (t->type == VARIABLE) {
    print_variable(fp, t);
    if (t->sym_num == 0)
      *prev = NAME_SYM;
    else
      *prev = (name_sym(sn_to_str(t->sym_num)) ? NAME_SYM : SYM_SYM);
  }

  else {  /* complex */
    str = sn_to_str(t->sym_num);
      
    if (str_ident(str, "$Quantified")) {  /* Quantified Formula */
      /* parens if parent is special op */
      if (n < 1000) {
      fprintf(fp, "("); *prev = OPEN_PAREN;
      }
      for (r = t->farg; r; r = r->narg) {
      /* parens if special op in child */
      write_term(fp, r->argval, 0, prev);
      if (r->narg) {
        fprintf(fp, " "); *prev = OTHER_PUNC;
      }
      }
      if (n < 1000) {
      fprintf(fp, ")"); *prev = OTHER_PUNC;
      }
    }   /* end Formula */

    else if (is_symbol(t, "$cons", 2)) {
      fprintf(fp, "["); *prev = OTHER_PUNC;
      write_term(fp, t->farg->argval, 1000, prev);
      t1 = t->farg->narg->argval;
      while (t1->sym_num == str_to_sn("$cons", 2)) {
      fprintf(fp, ","); *prev = OTHER_PUNC;
      write_term(fp, t1->farg->argval, 1000, prev);
      t1 = t1->farg->narg->argval;
      }
      if (t1->sym_num == str_to_sn("$nil", 0)) {
      fprintf(fp, "]"); *prev = OTHER_PUNC;
      }
      else {
      fprintf(fp, "|"); *prev = OTHER_PUNC;
      write_term(fp, t1, 1000, prev);
      fprintf(fp, "]"); *prev = OTHER_PUNC;
      }
    }   /* end list */
    else if (Flags[BIRD_PRINT].val &&is_symbol(t, "a", 2))
      bird_print(fp, t);

    else {
      s = sn_to_node(t->sym_num);

      if (s->special_op && s->arity == 2) {  /* infix */
      na1 = na2 = s->op_prec;
      if (s->op_type == XFX || s->op_type == XFY)
        na1--;
      if (s->op_type == XFX || s->op_type == YFX)
        na2--;
      if (s->op_prec > n) {
        fprintf(fp, "("); *prev = OPEN_PAREN;
      }
      write_term(fp, t->farg->argval, na1, prev);

      /* Decide on spaces around infix op. */

      if (name_sym(str))
        s1 = s2 = " ";
      else {
        if (*prev == OTHER_PUNC || *prev == NAME_SYM)
          s1 = "";
        else
          s1 = " ";
        next = next_token_type(t->farg->narg->argval, na2);
        if (next == OTHER_PUNC || next == NAME_SYM)
          s2 = "";
        else
          s2 = " ";
      }
            
      fprintf(fp, "%s%s%s", s1,str,s2);
      if (str_ident(s2, " "))
        *prev = OTHER_PUNC;
      else
        *prev = (name_sym(str) ? NAME_SYM : SYM_SYM);
      write_term(fp, t->farg->narg->argval, na2, prev);
      if (s->op_prec > n) {
        fprintf(fp, ")"); *prev = OTHER_PUNC;
      }
      }

      else if (s->special_op && s->arity == 1) {  /* prefix,postfix */
      na1 = s->op_prec;
      if (s->op_type == FX || s->op_type == XF)
        na1--;

      if (s->op_prec > n) {
        fprintf(fp, "("); *prev = OPEN_PAREN;
      }

      if (s->op_type == FX || s->op_type == FY) {
            
        /* Decide on spaces around special prefix op. */

        if (name_sym(str))
          s1 = s2 = " ";
        else {
          if (*prev == OTHER_PUNC || *prev == OPEN_PAREN)
            s1 = "";
          else
            s1 = " ";
          next = next_token_type(t->farg->argval, na1);
          if (next == OTHER_PUNC || next == OPEN_PAREN || next == NAME_SYM)
            s2 = "";
          else
            s2 = " ";
        }
            
        fprintf(fp, "%s%s%s", s1,str,s2);
        if (str_ident(s2, " "))
          *prev = OTHER_PUNC;
        else
          *prev = (name_sym(str) ? NAME_SYM : SYM_SYM);
        write_term(fp, t->farg->argval, na1, prev);
      }
      else {
        write_term(fp, t->farg->argval, na1, prev);

        /* Decide on spaces around special postfix op. */

        if (name_sym(str))
          s1 = s2 = " ";
        else {
          if (*prev == OTHER_PUNC || *prev == NAME_SYM)
            s1 = "";
          else
            s1 = " ";
          /* Can't easily tell next token, so just output space. */
          s2 = " ";
        }
            
        fprintf(fp, "%s%s%s", s1,str,s2);
        *prev = OTHER_PUNC;
      }

      if (s->op_prec > n) {
        fprintf(fp, ")"); *prev = OTHER_PUNC;
      }
      }

      else {  /* functor(args) */
      fprintf(fp, "%s", str);
      fprintf(fp, "("); *prev = OPEN_PAREN;
      r = t->farg;
      while(r != NULL) {
        write_term(fp, r->argval, 1000, prev);
        r = r->narg;
        if(r != NULL) {
          fprintf(fp, ","); *prev = OTHER_PUNC;
        }
      }
      fprintf(fp, ")"); *prev = OTHER_PUNC;
      }
    }
  }
}  /* write_term */

/*************
 *
 *    display_term(file_ptr, term)  --  Display a term in internal form.
 *
 *************/

void display_term(FILE *fp,
              struct term *t)
{
  struct rel *r;

  if (t == NULL)
    fprintf(fp, "<display_term gets NULL pointer>");
  else if (t->type == NAME) {
    fprintf(fp, "%s", sn_to_str(t->sym_num));
  }
  else if (t->type == VARIABLE)
    print_variable(fp, t);
  else {  /* complex */
    fprintf(fp, "%s", sn_to_str(t->sym_num));
    fprintf(fp, "(");
    r = t->farg;
    while(r != NULL) {
      display_term(fp, r->argval);
      r = r->narg;
      if(r != NULL)
      fprintf(fp, ",");
    }
    fprintf(fp, ")");
  }
}  /* display_term */

/*************
 *
 *    print_term(file_ptr, term)  --  Print a term to a file.
 *
 *    Flag determines write_term vs. display_term.
 *
 *************/

void print_term(FILE *fp,
            struct term *t)
{
  int i;

  if (Flags[DISPLAY_TERMS].val)
    display_term(fp, t);
  else {
    i = OTHER_PUNC;  /* Assume previous token is punctuation. */
    write_term(fp, t, 1000, &i);
  }
}  /* print_term */

/*************
 *
 *    p_term(term)  --  print_term and \n to the standard output.
 *
 *************/

void p_term(struct term *t)
{
  print_term(stdout, t);
  printf("\n");
  fflush(stdout);
}  /* p_term */

/*************
 *
 *    d_term(term)  --  display_term and \n to the standard output.
 *
 *************/

void d_term(struct term *t)
{
  display_term(stdout, t);
  printf("\n");
  fflush(stdout);
}  /* p_term */

/*************
 *
 *    print_term_nl(fp, term)  --  print_term followed by period and newline
 *
 *************/

void print_term_nl(FILE *fp,
               struct term *t)
{
  print_term(fp, t);
  fprintf(fp,".\n");
}  /* print_term_nl */

/*************
 *
 *   int print_term_length(t)
 *
 *************/

int print_term_length(struct term *t)
{
  static FILE *tfp = NULL;
  int i;
  char s[MAX_BUF];

  if (!tfp)
    tfp = tmpfile();

  rewind(tfp);
  print_term(tfp, t);
  fprintf(tfp, "%c", '\0');  /* end marker */
  fflush(tfp);
  rewind(tfp);

  for (i = 0, s[i]=getc(tfp); s[i] && i < MAX_BUF; s[++i]=getc(tfp));

#if 0
  printf("%d: ", i); print_term(stdout, t);
#endif

  return(i == MAX_BUF ? MAX_INT : i);

}  /* print_term_length */

/*************
 *
 *   pretty_print_term(fp, t, indents)
 *
 *************/

void  pretty_print_term(FILE *fp,
                  struct term *t,
                  int indents)
{
  int len, spaces_before_term, i;

  spaces_before_term = indents * Parms[PRETTY_PRINT_INDENT].val;
      
  for (i=0; i<spaces_before_term; i++)
    fprintf(fp, " ");

  if (t->type != COMPLEX)
    print_term(fp, t);
  else {
      
    len = print_term_length(t);
      
    if (spaces_before_term + len < 80)
      print_term(fp, t);
    else {
      struct rel *r;
          
      fprintf(fp, "%s", sn_to_str(t->sym_num));
      fprintf(fp, "(\n");
      r = t->farg;
      while(r) {
      pretty_print_term(fp, r->argval, indents+1);
      r = r->narg;
      if(r != NULL)
        fprintf(fp, ",");
      fprintf(fp, "\n");
      }
      for (i=0; i<spaces_before_term; i++)
      fprintf(fp, " ");
      fprintf(fp, ")");
    }
  }
}  /* pretty_print_term */

/*************
 *
 *   print_variable(fp, variable)
 *
 *************/

void print_variable(FILE *fp,
                struct term *t)
{
  int i;

  if (t->sym_num != 0)
    fprintf(fp, "%s", sn_to_str(t->sym_num));
  else if (Flags[PROLOG_STYLE_VARIABLES].val) {
    fprintf(fp, "%c", (t->varnum % 26) + 'A');
    i = t->varnum / 26;
    if (i > 0)
      fprintf(fp, "%d", i);
  }
  else {
    if (t->varnum <= 2)
      fprintf(fp, "%c", 'x'+t->varnum);
    else if (t->varnum <= 5)
      fprintf(fp, "%c", 'r'+t->varnum);
    else
      fprintf(fp, "%c%d", 'v', t->varnum);
  }
}  /* print_variable */

/*************
 *
 *    void built_in_symbols()
 *
 *    note: in a similar way, user-defined evaluable functions are declared
 *    in `declare_user_functions'.
 *
 *************/

void built_in_symbols(void)
{
  struct sym_ent *p;

  p = insert_sym("$cons", 2); Cons_sym_num = p->sym_num;
  p = insert_sym("$nil", 0);  Nil_sym_num = p->sym_num;
  p = insert_sym("$IGNORE", 1); Ignore_sym_num = p->sym_num;
  p = insert_sym("$CHR", 1); Chr_sym_num = p->sym_num;
  p = insert_sym("$dots", 1); Dots_sym_num = p->sym_num;
  p = insert_sym("$", 1);

  p = insert_sym("$SUM", 2);  p->eval_code = SUM_SYM;
  p = insert_sym("$PROD", 2); p->eval_code = PROD_SYM;
  p = insert_sym("$DIFF", 2); p->eval_code = DIFF_SYM;
  p = insert_sym("$DIV", 2);  p->eval_code = DIV_SYM;
  p = insert_sym("$MOD", 2);  p->eval_code = MOD_SYM;

  p = insert_sym("$EQ", 2);   p->eval_code = EQ_SYM;
  p = insert_sym("$NE", 2);   p->eval_code = NE_SYM;
  p = insert_sym("$LT", 2);   p->eval_code = LT_SYM;
  p = insert_sym("$LE", 2);   p->eval_code = LE_SYM;
  p = insert_sym("$GT", 2);   p->eval_code = GT_SYM;
  p = insert_sym("$GE", 2);   p->eval_code = GE_SYM;

  p = insert_sym("$AND", 2);  p->eval_code = AND_SYM;
  p = insert_sym("$OR", 2);   p->eval_code = OR_SYM;
  p = insert_sym("$NOT", 1);  p->eval_code = NOT_SYM;
  p = insert_sym("$TRUE", 1); p->eval_code = TRUE_SYM;
  p = insert_sym("$T", 0);    p->eval_code = T_SYM;
  p = insert_sym("$F", 0);    p->eval_code = F_SYM;

  p = insert_sym("$ID", 2);   p->eval_code = ID_SYM;
  p = insert_sym("$LNE", 2);  p->eval_code = LNE_SYM;
  p = insert_sym("$LLT", 2);  p->eval_code = LLT_SYM;
  p = insert_sym("$LLE", 2);  p->eval_code = LLE_SYM;
  p = insert_sym("$LGT", 2);  p->eval_code = LGT_SYM;
  p = insert_sym("$LGE", 2);  p->eval_code = LGE_SYM;

  p = insert_sym("$BIT_AND", 2);     p->eval_code = BIT_AND_SYM;
  p = insert_sym("$BIT_OR", 2);      p->eval_code = BIT_OR_SYM;
  p = insert_sym("$BIT_XOR", 2);     p->eval_code = BIT_XOR_SYM;
  p = insert_sym("$BIT_NOT", 1);     p->eval_code = BIT_NOT_SYM;
  p = insert_sym("$SHIFT_LEFT", 2);  p->eval_code = SHIFT_LEFT_SYM;
  p = insert_sym("$SHIFT_RIGHT", 2); p->eval_code = SHIFT_RIGHT_SYM;

  p = insert_sym("$INT_TO_BITS", 1);     p->eval_code = INT_TO_BITS_SYM;
  p = insert_sym("$BITS_TO_INT", 1);     p->eval_code = BITS_TO_INT_SYM;

  p = insert_sym("$IF", 3);          p->eval_code = IF_SYM;

  p = insert_sym("$NEXT_CL_NUM", 0); p->eval_code = NEXT_CL_NUM_SYM;
  p = insert_sym("$ATOMIC", 1);      p->eval_code = ATOMIC_SYM;
  p = insert_sym("$INT", 1);         p->eval_code = INT_SYM;
  p = insert_sym("$BITS", 1);        p->eval_code = BITS_SYM;
  p = insert_sym("$VAR", 1);         p->eval_code = VAR_SYM;
  p = insert_sym("$GROUND", 1);      p->eval_code = GROUND_SYM;
  p = insert_sym("$OUT", 1);         p->eval_code = OUT_SYM;

  p = insert_sym("$FSUM", 2);  p->eval_code = FSUM_SYM;
  p = insert_sym("$FPROD", 2); p->eval_code = FPROD_SYM;
  p = insert_sym("$FDIFF", 2); p->eval_code = FDIFF_SYM;
  p = insert_sym("$FDIV", 2);  p->eval_code = FDIV_SYM;

  p = insert_sym("$FEQ", 2);   p->eval_code = FEQ_SYM;
  p = insert_sym("$FNE", 2);   p->eval_code = FNE_SYM;
  p = insert_sym("$FLT", 2);   p->eval_code = FLT_SYM;
  p = insert_sym("$FLE", 2);   p->eval_code = FLE_SYM;
  p = insert_sym("$FGT", 2);   p->eval_code = FGT_SYM;
  p = insert_sym("$FGE", 2);   p->eval_code = FGE_SYM;

  p = insert_sym("$COMMON_EXPRESSION", 3); p->eval_code = COMMON_EXPRESSION_SYM;

  p = insert_sym("$RENAME", 2);      p->eval_code = RENAME_SYM;
  p = insert_sym("$UNIQUE_NUM", 0);  p->eval_code = UNIQUE_NUM_SYM;
  p = insert_sym("$OCCURS", 2);      p->eval_code = OCCURS_SYM;
  p = insert_sym("$VOCCURS", 2);     p->eval_code = VOCCURS_SYM;
  p = insert_sym("$VFREE", 2);       p->eval_code = VFREE_SYM;
}  /* built_in_symbols */

/*************
 *
 *    int declare_op(prec, type, str)
 *
 *************/

int declare_op(int prec,
             int type,
             char *str)
{
  int arity, sn, save_flag;
  struct sym_ent *p;

  if (prec < 1 || prec > 999)
    return(0);

  switch (type) {
  case FX:
  case FY:
  case XF:
  case YF: arity = 1; break;
  case XFX:
  case XFY:
  case YFX: arity = 2; break;
  default: return(0);
  }

  save_flag = Flags[CHECK_ARITY].val;
  Flags[CHECK_ARITY].val = 0;
  sn = str_to_sn(str, arity);
  Flags[CHECK_ARITY].val = save_flag;

  p = sn_to_node(sn);

  /* Don't check if it's already special.  Allow it to change. */

  p->special_op = 1;
  p->op_type = type;
  p->op_prec = prec;
  return(1);

}  /* declare_op */

/*************
 *
 *    init_special_ops()
 *
 *    Declare the built-in special operators.
 *
 *************/

void init_special_ops(void)
{
  int rc;

  rc = declare_op(800,  XFY, "#");

  rc = declare_op(800,  XFX, "->");
  rc = declare_op(800,  XFX, "<->");
  rc = declare_op(790,  XFY, "|");
  rc = declare_op(780,  XFY, "&");

  rc = declare_op(700,  XFX, "=");
  rc = declare_op(700,  XFX, "!=");

  rc = declare_op(700,  XFX, "<");
  rc = declare_op(700,  XFX, ">");
  rc = declare_op(700,  XFX, "<=");
  rc = declare_op(700,  XFX, ">=");
  rc = declare_op(700,  XFX, "==");
  rc = declare_op(700,  XFX, "=/=");

  rc = declare_op(700,  XFX, "@<");
  rc = declare_op(700,  XFX, "@>");
  rc = declare_op(700,  XFX, "@<=");
  rc = declare_op(700,  XFX, "@>=");

  rc = declare_op(500,  XFY, "+");
  rc = declare_op(500,  XFX, "-");

  rc = declare_op(500,   FX, "+");
  rc = declare_op(500,   FX, "-");

  rc = declare_op(400,  XFY, "*");
  rc = declare_op(400,  XFX, "/");

  rc = declare_op(300,  XFX, "mod");

#ifndef SINGLE_QUOTE
  rc = declare_op(300,  XF, "\'");
#endif

}  /* init_special_ops */

/*************
 *
 *    int process_op_command(t)
 *
 *************/

int process_op_command(struct term *t)
{
  int type, n, rc;
  struct term *t1, *t2;
  char *s;

  if (sn_to_arity(t->sym_num) != 3) {
    printf("op command must have arity 3.\n");
    return(0);
  }
  t1 = t->farg->argval;
  if (t1->type != NAME || !str_int(sn_to_str(t1->sym_num), &n) ||
      n < 1 || n > 999) {
    printf("\nERROR: first argument of op command must be 1..999.\n");
    return(0);
  }
  t1 = t->farg->narg->argval;
  s = sn_to_str(t1->sym_num);
  if (str_ident(s, "xfx") || str_ident(s, "infix"))
    type = XFX;
  else if (str_ident(s, "xfy") || str_ident(s, "infix_right"))
    type = XFY;
  else if (str_ident(s, "yfx") || str_ident(s, "infix_left"))
    type = YFX;
  else if (str_ident(s, "fx") || str_ident(s, "prefix"))
    type = FX;
  else if (str_ident(s, "xf") || str_ident(s, "postfix"))
    type = XF;
  else if (str_ident(s, "fy") || str_ident(s, "prefix_assoc"))
    type = FY;
  else if (str_ident(s, "yf") || str_ident(s, "postfix_assoc"))
    type = YF;
  else
    type = MAX_INT;

  if (type == MAX_INT || t1->type != NAME) {
    printf("\nERROR: second argument of op command must be xfx, xfy, yfx, xf, yf, fx, or fy.\n");
    return(0);
  }

  t1 = t->farg->narg->narg->argval;

  if (t1->type == NAME)
    rc = declare_op(n, type, sn_to_str(t1->sym_num));
  else if (proper_list(t1)) {
    for ( ; t1->type == COMPLEX; t1 = t1->farg->narg->argval) {
      t2 = t1->farg->argval;
      if (t2->type != NAME) {
      printf("\nERROR: list in op command must be all names.\n");
      return(0);
      }
      rc = declare_op(n, type, sn_to_str(t2->sym_num));
    }
  }
  else {
    printf("\nERROR: third argument of op command must be a name or a list.\n");
    return(0);
  }
  return(1);
}  /* process_op_command */

/*************
 *
 *    void fill_in_op_data(p, t)
 *
 *************/

static void fill_in_op_data(struct sequence_member *p,
                      struct term *t)
{
  struct sym_ent *nd;
  char *str;
  int i, flag;

  p->t = t;
  p->binary_type = p->unary_type = 0;
  p->binary_prec = p->unary_prec = 0;

  if (t->type == NAME) {
    str = sn_to_str(t->sym_num);
    for (i = flag = 0; i < SYM_TAB_SIZE && flag < 2; i++) {
      for (nd = Sym_tab[i]; nd && flag < 2; nd = nd->next) {
      if (str_ident(str, nd->name) && nd->special_op) {
        if (nd->arity == 1) {
          p->unary_type = nd->op_type;
          p->unary_prec = nd->op_prec;
        }
        else {  /* must be binary */
          p->binary_type = nd->op_type;
          p->binary_prec = nd->op_prec;
        }
      }
      }
    }
  }

}  /* fill_in_op_data */

/*************
 *
 *    int is_white(c) -- including start-of-comment '%'.
 *
 *************/

static int is_white(char c)
{
  return(c == ' ' ||
       c == '\t' ||  /* tab */
       c == '\n' ||  /* newline */
       c == '\v' ||  /* vertical tab */
       c == '\r' ||  /* carriage return */
       c == '\f' ||  /* form feed */
       c == '%');
}  /* is_white */

/*************
 *
 *    skip_white(buffer, position)
 *
 *    Advance the pointer to the next nonwhite, noncomment position.
 *
 *************/

void skip_white(char *buf,
            int *p)
{
  char c;
  c = buf[*p];
  while (is_white(c)) {
    if (c == '%')  /* skip over comment */
      while (buf[++(*p)] != '\n' && buf[*p] != '\0') ;
    if (buf[*p] == '\0')
      c = '\0';
    else
      c = buf[++(*p)];
  }
}  /* skip_white */

/*************
 *
 *    int is_symbol_char(c, in_list)
 *
 *************/

static int is_symbol_char(char c,
                    int in_list)
{
  return(c == '+' ||
       c == '-' ||
       c == '*' ||
       c == '/' ||
       c == '\\' ||
       c == '^' ||
       c == '<' ||
       c == '>' ||
       c == '=' ||
       c == '`' ||
       c == '~' ||
       c == ':' ||
       c == '?' ||
       c == '@' ||
       c == '&' ||
      
       (c == '|' && !in_list) ||
#ifndef SINGLE_QUOTE
       c == '\'' ||
#endif
       c == '!' ||
       c == '#' ||
       c == ';'    );

}  /* is_symbol_char */

/*************
 *
 *    int quote_char(c)
 *
 *************/

static int quote_char(char c)
{
  return(
#ifdef SINGLE_QUOTE
       c == '\'' ||
#endif
       c == '\"');
       
}  /* quote_char */

/*************
 *
 *    int is_alpha_numeric(c) -- including _ and $
 *
 *************/

static int is_alpha_numeric(char c)
{
  return((c >= '0' && c <= '9') ||
       (c >= 'a' && c <= 'z') ||
       (c >= 'A' && c <= 'Z') ||
       c == '_' ||
       c == '$');
}  /* is_alpha_numeric */

/*************
 *
 *    int name_sym(s)
 *
 *************/

int name_sym(char *s)
{
  if (quote_char(*s))
    return(1);  /* quoted string ok */
  else {
    for ( ; *s; s++)
      if (!is_alpha_numeric(*s))
      return(0);
    return(1);
  }
}  /* name_sym */

/*************
 *
 *    get_name(buffer, position, name, in_list)
 *
 *************/

static void get_name(char *buf,
                 int *p,
                 char *name,
                 int in_list)
{
  int i, ok, okq;
  char c, q;

  i = 0; ok = 1; okq = 1;
  skip_white(buf, p);
  c = buf[*p];
  if (is_alpha_numeric(c)) {
    while ((ok = i < MAX_NAME-1) && is_alpha_numeric(c)) {
      name[i++] = c;
      c = buf[++(*p)];
    }
  }
  else if (is_symbol_char(c, in_list)) {
    while ((ok = i < MAX_NAME-1) && is_symbol_char(c, in_list)) {
      name[i++] = c;
      c = buf[++(*p)];
    }
  }
  else if (quote_char(c)) {
    q = c;
    name[i++] = c;
    c = buf[++(*p)];
    while ((ok = i < MAX_NAME-1) && c != q && (okq = c != '\0')) {
      name[i++] = c;
      c = buf[++(*p)];
    }
    if (okq) {
      name[i++] = c;  /* quote char */
      ++(*p);
    }
  }

  if (!ok) {
    fprintf(stdout, "\nERROR, name too big, max is %d; ", MAX_NAME-1);
    name[0] = '\0';
  }
  else if (!okq) {
    fprintf(stdout, "\nERROR, quoted name has no end; ");
    name[0] = '\0';
  }
  else
    name[i] = '\0';
}  /* get_name */

/*************
 *
 *    print_error(fp, buf, pos)
 *
 *************/

void print_error(FILE *fp,
             char *buf,
             int pos)
{
#if 0
  int i;

  fprintf(fp, "%s\n", buf);
  for (i = 0; i < pos; i++) {
    if (buf[i] == '\t')
      fprintf(fp, "--------");  /* doesn't always work */
    else if (buf[i] == '\n')
      fprintf(fp, "\n");
    else
      fprintf(fp, "-");
  }
  fprintf(fp, "^\n");
#else
  int i;
  i = 0;
  if (buf[0] == '\n')
    i = 1;
  while (i < pos) {
    if (buf[i] == '%')  /* skip over comment */
      while (buf[++i] != '\n') ;
    fprintf(fp, "%c", buf[i++]);
  }
  fprintf(fp, " ***HERE*** ");

  while (buf[i]) {
    if (buf[i] == '%')  /* skip over comment */
      while (buf[++i] != '\n') ;
    fprintf(fp, "%c", buf[i++]);
  }
  fprintf(fp, "\n");

#endif
}  /* print_error */

/* We need this declaration, because seq_to_term is mutually recursive
   with seq_to_quant_term
*/

static struct term *seq_to_term(struct sequence_member *seq,
                        int start,
                        int end,
                        int m);

/*************
 *
 *    struct term *seq_to_quant_term(seq, n)
 *
 *    Take a sequence of terms t1,...,tn and build term $Quantified(t1,...,tn).
 *    t1 is already known to be a quantifier, and n >= 3.
 *    Check that t2,...,tn-1 are all names.
 *    On success, the resulting term is an entirely new copy.
 *
 *************/

static struct term *seq_to_quant_term(struct sequence_member *seq,
                              int n)
{
  struct rel *r_prev, *r_new;
  struct term *t, *t1;
  int i;

  if (n == 1)
    return(NULL);

  for (i = 1; i < n-1; i++)
    if (seq[i].t->type != NAME)
      return(NULL);

  /* Special case: negated formula need not be parenthesized.
   * For example, all x -p(x) is OK.  In this case, the sequence is
   * [all, x, -, p(x)], so we must adjust things.
   */

  if (str_ident(sn_to_str(seq[n-2].t->sym_num), "-")) {
    if (n == 3)
      return(NULL);  /* all - p */
    else {
      struct term *t;
      t = seq_to_term(seq, n-2, n-1, 1000);
      printf("adjusted term: "); p_term(t);
      if (t) {
      zap_term(seq[n-2].t);
      zap_term(seq[n-1].t);
      fill_in_op_data(&seq[n-2], t);
      /* caller will still think there are n terms */
      seq[n-1].t = NULL;
      n--;
      }
      else
      return(NULL);
    }
  }

  t = get_term();
  t->type = COMPLEX;
  t->sym_num = str_to_sn("$Quantified", n);
  for (i = 0, r_prev = NULL; i < n; i++) {
    r_new = get_rel();
    if (!r_prev)
      t->farg = r_new;
    else
      r_prev->narg = r_new;
    t1 = copy_term(seq[i].t);
    r_new->argval = t1;
    r_prev = r_new;
  }
  return(t);

}  /* seq_to_quant_term */

/*************
 *
 *    struct term *seq_to_term(seq, start, end, m)
 *
 *    seq is an array of terms/operators, and start and end are
 *    indexes into seq.  This routine attempts to construct a term
 *    starting with start, ending with end, with precedence <= m.
 *    On success, the resulting term is an entirely new copy.
 *
 *************/

static struct term *seq_to_term(struct sequence_member *seq,
                   int start,
                   int end,
                   int m)
{
  int i, n, type;
  struct term *t1, *t2, *t3, *t;
  struct rel *r1, *r2;

  if (start == end) {
    t = copy_term(seq[start].t);
    return(t);
  }
  else {

    /* Check if first is prefix op that applies to rest. */

    if (seq[start].t->type == NAME) {
      type = seq[start].unary_type;
      n = seq[start].unary_prec;
      t = seq[start].t;
      
      if (type == FX && n <= m) {
      t1 = seq_to_term(seq, start+1, end, n-1);
      if (t1) {
        t3 = get_term();
        t3->type = COMPLEX;
        t3->sym_num = str_to_sn(sn_to_str(t->sym_num), 1);
        r1 = get_rel();
        t3->farg = r1;
        r1->argval = t1;
        return(t3);
      }
      }
      else if (type == FY && n <= m) {
      t1 = seq_to_term(seq, start+1, end, n);
      if (t1) {
        t3 = get_term();
        t3->type = COMPLEX;
        t3->sym_num = str_to_sn(sn_to_str(t->sym_num), 1);
        r1 = get_rel();
        t3->farg = r1;
        r1->argval = t1;
        return(t3);
      }
      }
    }

    /* Check if last is postfix op that applies to all preceding. */

    if (seq[end].t->type == NAME) {
      type = seq[end].unary_type;
      n = seq[end].unary_prec;
      t = seq[end].t;

      if (type == XF && n <= m) {
      t1 = seq_to_term(seq, start, end-1, n-1);
      if (t1) {
        t3 = get_term();
        t3->type = COMPLEX;
        t3->sym_num = str_to_sn(sn_to_str(t->sym_num), 1);
        r1 = get_rel();
        t3->farg = r1;
        r1->argval = t1;
        return(t3);
      }
      }
      else if (type == YF && n <= m) {
      t1 = seq_to_term(seq, start, end-1, n);
      if (t1) {
        t3 = get_term();
        t3->type = COMPLEX;
        t3->sym_num = str_to_sn(sn_to_str(t->sym_num), 1);
        r1 = get_rel();
        t3->farg = r1;
        r1->argval = t1;
        return(t3);
      }
      }
    }
            
    /* Look for an infix operator. */

    for (i = start+1; i <= end-1; i++) {
      if (seq[i].t->type == NAME) {
      type = seq[i].binary_type;
      n = seq[i].binary_prec;
      t = seq[i].t;

      if (type == XFY && n <= m) {
        t1 = seq_to_term(seq, start, i-1, n-1);
        if (t1) {
          t2 = seq_to_term(seq, i+1, end, n);
          if (!t2)
            zap_term(t1);
        }
        if (t1 && t2) {
          t3 = get_term();
          t3->type = COMPLEX;
          t3->sym_num = str_to_sn(sn_to_str(t->sym_num), 2);
          r1 = get_rel(); r2 = get_rel();
          t3->farg = r1; r1->narg = r2;
          r1->argval = t1; r2->argval = t2;
          return(t3);
        }
      }
      else if (type == YFX && n <= m) {
        t1 = NULL;
        t2 = seq_to_term(seq, i+1, end, n-1);
        if (t2) {
          t1 = seq_to_term(seq, start, i-1, n);
          if (!t1)
            zap_term(t2);
        }
        if (t1 && t2) {
          t3 = get_term();
          t3->type = COMPLEX;
          t3->sym_num = str_to_sn(sn_to_str(t->sym_num), 2);
          r1 = get_rel(); r2 = get_rel();
          t3->farg = r1; r1->narg = r2;
          r1->argval = t1; r2->argval = t2;
          return(t3);
        }
      }
      else if (type == XFX && n <= m) {
        t1 = seq_to_term(seq, start, i-1, n-1);
        t2 = NULL;
        if (t1) {
          t2 = seq_to_term(seq, i+1, end, n-1);
          if (!t2)
            zap_term(t1);
        }
        if (t1 && t2) {
          t3 = get_term();
          t3->type = COMPLEX;
          t3->sym_num = str_to_sn(sn_to_str(t->sym_num), 2);
          r1 = get_rel(); r2 = get_rel();
          t3->farg = r1; r1->narg = r2;
          r1->argval = t1; r2->argval = t2;
          return(t3);
        }
      }
      }  /* name */
    }  /* loop looking for infix op to apply */
      
    return(NULL);
  }
}  /* seq_to_term */

/*************
 *
 *    struct term_ptr *str_to_args(buffer, position, name)
 *
 *    name -- the functor.
 *
 *    start: functor(  a1 , a2 , a3 )
 *                   ^
 *    end:   functor(  a1 , a2 , a3 )
 *                                  ^
 *************/

static struct term *str_to_args(char *buf,
                        int *p,
                        char *name)
{
  struct term *t, *t_sub;
  struct rel *r1, *r2;
  int i;

  t = get_term();
  t->type = COMPLEX;
  r1 = NULL;
  i = 0;  /* count subterms to get arity */

  while (buf[*p] != ')') {
    i++;
    t_sub = str_to_term(buf, p, 0);
    if (t_sub == NULL)
      return(NULL);
    else if (buf[*p] != ',' && buf[*p] != ')') {
      fprintf(stdout, "\nERROR, comma or ) expected:\n");
      print_error(stdout, buf, *p);
      return(NULL);
    }
    else {
      r2 = get_rel();
      r2->argval = t_sub;
      if (r1 == NULL)
      t->farg = r2;
      else
      r1->narg = r2;
      r1 = r2;
      if (buf[*p] == ',')
      (*p)++;          /* step past comma */
    }
  }
  if (i == 0) {
    fprintf(stdout, "\nERROR, functor has no arguments:\n");
    print_error(stdout, buf, *p);
    return(NULL);
  }

  t->sym_num = str_to_sn(name, i);  /* functor */
  return(t);

}  /* str_to_args */

/*************
 *
 *    struct term_ptr *str_to_list(buffer, position)
 *
 *    start: [ a1 , a2 , a3 ]
 *           ^
 *    end:   [ a1 , a2 , a3 ]
 *                           ^
 *************/

static struct term *str_to_list(char *buf,
                        int *p)
{
  struct term *t_cons, *t_head, *t_tail, *t_return;
  struct rel *r_head, *r_tail;
  int go;

  (*p)++;  /* step past '[' */

  if (buf[*p] == ']') {                        /* [] */
    t_return = get_term();
    t_return->type = NAME;
    t_return->sym_num = str_to_sn("$nil", 0);
    (*p)++;  /* skip "]" */
    return(t_return);
  }
  else {                           /* [h|t], [t1,...,tn], or [t1,...,tn|t] */
    t_return = NULL; r_tail = NULL;
    go = 1;
      
    while (go) {
      t_head = str_to_term(buf, p, 1);
      if (t_head == NULL)
      return(NULL);  /* error */
      t_cons = get_term();
      if (r_tail == NULL)
      t_return = t_cons;
      else
      r_tail->argval = t_cons;
      t_cons->type = COMPLEX;
      t_cons->sym_num = str_to_sn("$cons", 2);
      r_head = get_rel();
      t_cons->farg = r_head;
      r_head->argval = t_head;
      r_tail = get_rel();
      r_head->narg = r_tail;
      go = (buf[*p] == ',');
      if (go)
      (*p)++;  /* step past ',' */
    }
      
    if (buf[*p] == ']') {
      t_tail = get_term();
      r_tail->argval = t_tail;
      t_tail->type = NAME;
      t_tail->sym_num = str_to_sn("$nil", 0);
      (*p)++;  /* step past ']' */
      return(t_return);
    }
    else if (buf[*p] == '|') {
      (*p)++;  /* step past '|' */
      t_tail = str_to_term(buf, p, 1);
      if (buf[*p] != ']') {
      fprintf(stdout, "\nERROR, ']' expected in list:\n");
      print_error(stdout, buf, *p);
      return(NULL);
      }
      r_tail->argval = t_tail;
      (*p)++;  /* step past ']' */
      return(t_return);
    }
    else {
      fprintf(stdout, "\nERROR, ], |, or comma expected in list:\n");
      print_error(stdout, buf, *p);
      return(NULL);
    }
  }
}  /* str_to_list */

/*************
 *
 *    int str_to_sequence(buffer, position, seq, in_list)
 *
 *    Read a sequence of operators/terms---It will be parsed into
 *    a term later in str_to_term.
 *    After successful call, position is the delimeter following the term.
 *
 *    Mutually recursive with str_to_term.
 *
 *    If success, return the number of terms read.
 *
 *    If a syntax error is found, print message and return(0).
 *
 *************/

static int str_to_sequence(char *buf,
                     int *p,
                     struct sequence_member *seq,
                     int in_list)
{
  char name[MAX_NAME], c;
  struct term *t;
  int done, n, white;;

  done = 0; n = 0;
  while (!done) {
      
    get_name(buf, p, name, in_list);
    white = is_white(buf[*p]);  /* f(a) vs. f (a) */
    skip_white(buf, p);
      
    if (name[0] == '\0' && buf[*p] != '[' && buf[*p] != '(' && buf[*p] != '{') {
      fprintf(stdout, "\nERROR, name expected:\n");
      print_error(stdout, buf, *p);
      return(0);
    }
      
    else if (name[0] == '\0' && buf[*p] == '(') {         /* (term) */
      (*p)++;  /* step past '(' */
      t = str_to_term(buf, p, 0);
      if (t == NULL)
      return(0);
      if (buf[*p] != ')') {
      fprintf(stdout, "\nERROR, ')' expected:\n");
      print_error(stdout, buf, *p);
      return(0);
      }
      (*p)++;  /* step past ')' */
    }
      
    else if (name[0] == '\0' && buf[*p] == '{') {         /* {term} */
      (*p)++;  /* step past '{' */
      t = str_to_term(buf, p, 0);
      if (t == NULL)
      return(0);
      if (buf[*p] != '}') {
      fprintf(stdout, "\nERROR, '}' expected:\n");
      print_error(stdout, buf, *p);
      return(0);
      }
      (*p)++;  /* step past '}' */
    }
      
    else if (name[0] == '\0' && buf[*p] == '[') {           /* list */
      t = str_to_list(buf, p);
      if (t == NULL)
      return(0);
    }
      
    else if (name[0] != '\0' && !white && buf[*p] == '(')  /* f(args) */
      {
      (*p)++;  /* step past '(' */
      t = str_to_args(buf, p, name);
      if (t == NULL)
        return(0);
      (*p)++;  /* step past ')' */
      }
      
    else if (name[0] != '\0') {                           /* name */
      t = get_term();
      t->type = NAME;
      /* If it's an operator, change arity later. */
      t->sym_num = str_to_sn(name, 0);
    }
      
    else {
      fprintf(stdout, "\nERROR, unrecognized error in term:\n");
      print_error(stdout, buf, *p);
      return(0);
    }
      
    /* We have a term t. */
      
    if (n == MAX_COMPLEX) {
      fprintf(stdout, "\nERROR, term too big:\n");
      print_error(stdout, buf, *p);
      return(0);
    }
    else {
      fill_in_op_data(&seq[n], t);
      n++;
    }
      
    skip_white(buf, p);
    c = buf[*p];
    done = (c == ',' || c == ')' || c == '}' || c == ']' ||
          c == '.' || c == '\0' || (in_list && c == '|'));
  }
  return(n);
}  /* str_to_sequence */

/*************
 *
 *    struct term *str_to_term(buffer, position, in_list)
 *
 *    Parse a string and build a term.
 *    Mutually recursive with str_to_sequence.
 *    After successful call, position is the delimeter following the term.
 *
 *    If a syntax error is found, print message and return(NULL).
 *
 *************/

struct term *str_to_term(char *buf,
                   int *p,
                   int in_list)
{
  struct sequence_member seq[MAX_COMPLEX];
  struct term *t;
  int n, i, save_pos;

  save_pos = *p;

  n = str_to_sequence(buf, p, seq, in_list);
  if (n == 0)
    return(NULL);

  else if (seq[0].t->type == NAME && n > 2 &&
         (str_ident(sn_to_str(seq[0].t->sym_num), "all") ||
          str_ident(sn_to_str(seq[0].t->sym_num), "exists"))) {
    t = seq_to_quant_term(seq, n);
    if (!t) {
      fprintf(stdout, "\nERROR in quantifier prefix starting here:\n");
      print_error(stdout, buf, save_pos);
    }
  }

  else {
    t = seq_to_term(seq, 0, n-1, 1000);
      
    if (!t) {
      fprintf(stdout, "\nERROR, the %d terms/operators in the following sequence are OK, but they\ncould not be combined into a single term with special operators.\n", n);
      for (i = 0; i < n; i++)
      { p_term(seq[i].t); printf("  ");}
      printf("\n");
      fprintf(stdout, "The context of the bad sequence is:\n");
      print_error(stdout, buf, save_pos);
    }
  }

  for (i = 0; i < n; i++)
    if (seq[i].t != NULL)
      zap_term(seq[i].t);
  return(t);
}  /* str_to_term */

/*************
 *
 *     int read_buf(file_ptr, buffer)
 *
 *    Read characters into buffer until one of the following:
 *        1.  '.' is reached ('.' goes into the buffer)
 *        2.  EOF is reached:  buf[0] = '\0' (an error occurs if
 *                 any nonwhite space precedes EOF)
 *        3.  MAX_BUF characters have been read (an error occurs)
 *
 *    If error occurs, return(0), else return(1).
 *
 *************/

int read_buf(FILE *fp,
           char *buf)
{
  int c, qc, i, j, ok, eof, eof_q, max, max_q;

  ok = eof = eof_q = max = max_q = 0;  /* stop conditions */
  i = 0;

  while (!ok && !eof && !eof_q && !max && !max_q) {

    c = getc(fp);
    if (c == '%') {  /* comment--discard rest of line */
      while (c != '\n' && c != EOF)
      c = getc(fp);
    }
    if (c =='.')
      ok = 1;
    else if (c == EOF)
      eof = 1;
    else if (i == MAX_BUF-1)
      max = 1;
    else {
      buf[i++] = c;
      if (quote_char(c)) {
      qc = c;
      c = getc(fp);
      while (c != qc && c != EOF && i != MAX_BUF-1) {
        buf[i++] = c;
        c = getc(fp);
      }
      if (i == MAX_BUF-1)
        max_q = 1;
      else if (c == EOF)
        eof_q = 1;
      else
        buf[i++] = c;
      }
    }
  }

  if (ok) {
    buf[i++] = '.';
    buf[i] = '\0';
    return(1);
  }
  else if (eof) {
    /* white space at end of file is OK */
    j = 0;
    buf[i] = '\0';
    skip_white(buf, &j);
    if (i != j) {
      fprintf(stdout, "\nERROR, characters after last period: %s\n", buf);
      buf[0] = '\0';
      return(0);
    }
    else {
      buf[0] = '\0';
      return(1);
    }
  }
  else if (eof_q) {
    char s[500];
    buf[i>100 ? 100 : i] = '\0';
    sprintf(s, "read_buf, quoted string has no end:%s", buf);
    abend(s);
  }
  else if (max) {
    char s[500];
    buf[i>100 ? 100 : i] = '\0';
    sprintf(s, "read_buf, input string has more than %d characters, increase MAX_BUF", MAX_BUF);
    abend(s);
  }
  else {  /* max_q */
    char s[500];
    buf[i>100 ? 100 : i] = '\0';
    sprintf(s, "read_buf, input string (which contains quote mark) has more than %d characters, increase MAX_BUF", MAX_BUF);
    abend(s);
  }
  return(0);  /* to quiet lint */
}  /* read_buf */

/*************
 *
 *    struct term *term_fixup(t)
 *
 *    change !=(a,b) to -(=(a,b))
 *    change -(3)    to -3              not recursive, -(-(3)) -> -(-3))
 *    change +(3)    to +3              not recursive, +(+(3)) +> +(+3))
 *
 *************/

struct term *term_fixup(struct term *t)
{
  struct rel *r, *r1;
  struct term *t1;
  int neg;
  char *s, str[MAX_NAME];
  long l;

  if (t->type == COMPLEX) {
    if (is_symbol(t, "!=", 2)) {
      t1 = get_term(); t1->type = COMPLEX;
      r1 = get_rel();
      t1->farg = r1;
      r1->argval = t;
      t1->sym_num = str_to_sn("-", 1);
      t->sym_num = str_to_sn("=", 2);
      t = t1;
    }

    else if ((neg = is_symbol(t, "-", 1)) || is_symbol(t, "+", 1)) {
      t1 = t->farg->argval;
      s = sn_to_str(t1->sym_num);
      if (t1->type == NAME && str_long(s, &l)) {
      cat_str((neg ? "-" : "+"), s, str);
      t1->sym_num = str_to_sn(str, 0);
      free_rel(t->farg);
      free_term(t);
      t = t1;
      }
    }

    for (r = t->farg; r; r = r->narg)
      r->argval = term_fixup(r->argval);

  }
  return(t);
}  /* term_fixup */

/*************
 *
 *    struct term *term_fixup_2(t)
 *
 *    change  -(=(a,b)) to !=(a,b)
 *
 *************/

struct term *term_fixup_2(struct term *t)
{
  struct term *t1;
  struct rel *r;

  if (is_symbol(t, "-", 1) && is_symbol(t->farg->argval, "=", 2)) {
    t1 = t->farg->argval;
    t1->sym_num = str_to_sn("!=", 2);
    free_rel(t->farg);
    free_term(t);
    t = t1;
  }

  if (t->type == COMPLEX)
    for (r = t->farg; r; r = r->narg)
      r->argval = term_fixup_2(r->argval);

  return(t);
}  /* term_fixup_2 */

/*************
 *
 *    struct term *read_term(file_ptr, retcd_ptr) --
 *
 *    Read and return then next term.
 *    It is assumed that the next term in the file is terminated
 *    with a period.   NULL is returned if EOF is reached first.
 *
 *    If an error is found, return(0); else return(1).
 *
 *************/

struct term *read_term(FILE *fp,
                   int *rcp)
{
  char buf[MAX_BUF+1];  /* one extra for \0 at end */
  int p, rc;
  struct term *t;

  rc = read_buf(fp, buf);
  if (rc == 0) {  /* error */
    *rcp = 0;
    return(NULL);
  }
  else if (buf[0] == '\0') {  /* ok. EOF */
    *rcp = 1;
    return(NULL);
  }
  else {
    p = 0;
    t = str_to_term(buf, &p, 0);
    if (t == NULL) {
      *rcp = 0;
      return(NULL);
    }
    else {
      skip_white(buf, &p);
      if (buf[p] != '.') {
      fprintf(stdout, "\nERROR, text after term:\n");
      print_error(stdout, buf, p);
      *rcp = 0;
      return(NULL);
      }
      else {
      t = term_fixup(t);
      *rcp = 1;
      return(t);
      }
    }
  }
}  /* read_term */

/*************
 *
 *    merge_sort
 *
 *************/

void merge_sort(void **a,
            void **w,
            int start,
            int end,
            int (*comp_proc)(void *v1, void *v2))
{
  int mid, i, i1, i2, e1, e2;

  if (start < end) {
    mid = (start+end)/2;
    merge_sort(a, w, start, mid, comp_proc);
    merge_sort(a, w, mid+1, end, comp_proc);
    i1 = start; e1 = mid;
    i2 = mid+1; e2 = end;
    i = start;
    while (i1 <= e1 && i2 <= e2) {
      if ((*comp_proc)(a[i1], a[i2]) == LESS_THAN)
      w[i++] = a[i1++];
      else
      w[i++] = a[i2++];
    }

    if (i2 > e2)
      while (i1 <= e1)
      w[i++] = a[i1++];
    else
      while (i2 <= e2)
      w[i++] = a[i2++];

    for (i = start; i <= end; i++)
      a[i] = w[i];
  }
}  /* merge_sort */

/*************
 *
 *   compare_for_auto_lex_order()
 *
 *   First sort on arity:  0 < MAX_INT < ... < 3 < 2 < 1.
 *   Within arity, use strcmp function
 *
 *************/

int compare_for_auto_lex_order(void *d1,
                         void *d2)
{
  struct sym_ent *p1, *p2;
  int i;

  p1 = (struct sym_ent *) d1;
  p2 = (struct sym_ent *) d2;

  if (p1->arity == p2->arity) {
    i = strcmp(p1->name, p2->name);
    if (i < 0)
      return(LESS_THAN);
    else if (i > 0)
      return(GREATER_THAN);
    else {
      char s[500];
      sprintf(s, "compare_for_auto_lex_order, strings the same: %s.", p1->name);
      abend(s);
      return(0);  /* to quiet lint */
    }
  }

  else if (p1->arity == 0)
    return(LESS_THAN);
  else if (p2->arity == 0)
    return(GREATER_THAN);
  else if (p1->arity < p2->arity)
    return(GREATER_THAN);
  else
    return(LESS_THAN);
}  /* compare_for_auto_lex_order */

/*************
 *
 *   auto_lex_order()
 *
 *   Order the symbols in the symbol table using the lex_val field.
 *
 *************/

void auto_lex_order(void)
{
  int i, j, n;
  struct sym_ent *p;
  struct sym_ent **a, **w;

  /* Find an upper limit on the number of symbols. */
  n = new_sym_num();  /* don't use this for a sym_num */
  /* There should be at most n-1 symbols. */

  /* Allocate arrays for storing and for work. */

  a = (struct sym_ent **) tp_alloc(n * (int) sizeof(struct sym_ent *));
  w = (struct sym_ent **) tp_alloc(n * (int) sizeof(struct sym_ent *));

  for (i = j = 0; i < SYM_TAB_SIZE; i++)
    for (p = Sym_tab[i]; p; p = p->next)
      a[j++] = p;

  /* We find j symbols. */

#if 0
  printf("\nauto_lex_order: new_sym_num=%d, count=%d.\n\n", n, j);
#endif

  merge_sort((void **) a, (void **) w, 0, j-1, compare_for_auto_lex_order);

  /* Symbols get lex vals 2, 4, 6, 8, ... . */

  for (i = 0; i < j; i++) {
    a[i]->lex_val = i*2 + 2;
#if 0
    printf("%7s %d %d\n", a[i]->name, a[i]->arity, i);
#endif
  }

}  /* auto_lex_order */


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