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gretl_list.c

/* 
 *  gretl -- Gnu Regression, Econometrics and Time-series Library
 *  Copyright (C) 2001 Allin Cottrell and Riccardo "Jack" Lucchetti
 * 
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 * 
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 * 
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 * 
 */

#include "libgretl.h"
#include "gretl_list.h"
#include "gretl_func.h"
#include "libset.h"
#include "gretl_xml.h"

#define LDEBUG 0

typedef struct saved_list_ saved_list;

struct saved_list_ {
    char name[VNAMELEN];
    int *list;
    int level;
};

enum {
    LIST_OMIT_TIGHT,
    LIST_OMIT_SLOPPY
};

static saved_list **list_stack;
static int n_lists;

static int *real_gretl_list_omit (const int *orig, const int *omit, 
                          int minpos, int mode, int *err);

static saved_list *saved_list_new (const int *list, const char *name)
{
    saved_list *sl = malloc(sizeof *sl);

    if (sl != NULL) {
      sl->level = gretl_function_depth();
      if (list != NULL && list[0] > 0) {
          sl->list = gretl_list_copy(list);
      } else {
          sl->list = gretl_null_list();
      }
      if (sl->list == NULL) {
          free(sl);
          sl = NULL;
      } else {
          *sl->name = 0;
          strncat(sl->name, name, VNAMELEN - 1);
      }
    }

    return sl;
}

static void free_saved_list (saved_list *sl)
{
    if (sl != NULL) {
      free(sl->list);
      free(sl);
    }
}

static saved_list *get_saved_list_by_name (const char *name)
{
    saved_list *sl = NULL;
    int fsd = gretl_function_depth();
    int i;

    for (i=0; i<n_lists; i++) {
      if (!strcmp(name, list_stack[i]->name) && 
          fsd == list_stack[i]->level) {
          sl = list_stack[i];
          break;
      }
    }

    return sl;
}

/**
 * n_saved_lists:
 *
 * Returns: the number of saved (named) lists currently defined.
 */

int n_saved_lists (void)
{
    return n_lists;
}

/**
 * max_varno_in_saved_lists:
 *
 * Returns: the highest ID number of a variable referenced
 * in a saved (named) list.
 */

int max_varno_in_saved_lists (void)
{
    int *list;
    int i, j, vmax = 0;

    for (i=0; i<n_lists; i++) {
      list = list_stack[i]->list;
      for (j=1; j<=list[0]; j++) {
          if (list[j] > vmax) {
            vmax = list[j];
          }
      }
    }    

    return vmax;
}

/**
 * get_list_name_by_index:
 * @idx: 0-based index into array of saved lists.
 *
 * Returns: the name of the specified saved list, or %NULL if
 * @idx is out of bounds.
 */

const char *get_list_name_by_index (int idx)
{
    if (idx >= 0 && idx < n_lists) {
      return list_stack[idx]->name;
    } else {
      return NULL;
    }
}

/**
 * get_list_by_name:
 * @name: the name of the list to be found.
 *
 * Looks up @name in the stack of saved lists, at the current level
 * of function execution, and retrieves the associated list.
 *
 * Returns: the list, or %NULL if the lookup fails. 
 */

int *get_list_by_name (const char *name)
{
    int *ret = NULL;
    saved_list *sl;

    if (name != NULL) {
      sl = get_saved_list_by_name(name);
      if (sl != NULL) {
          ret = sl->list;
      }
    }

    return ret;
}

/**
 * append_to_list_by_name:
 * @targ: the name of the target list.
 * @add: list to add.
 *
 * If @targ is the name of a saved list, append the list
 * @add to it.
 *
 * Returns: 0 on success, non-zero code on failure.
 */

int append_to_list_by_name (const char *targ, const int *add)
{
    saved_list *sl = get_saved_list_by_name(targ);
    int err = 0;

    if (sl == NULL) {
      err = E_UNKVAR;
    } else {
      int *tmp = gretl_list_copy(sl->list);

      if (tmp == NULL) {
          err = E_ALLOC;
      } else {
          err = gretl_list_add_list(&tmp, add);
          if (!err) {
            free(sl->list);
            sl->list = tmp;
          }
      }
    } 

    return err;
}

/**
 * subtract_from_list_by_name:
 * @targ: the name of the target list.
 * @sub: sub-list to remove.
 *
 * If @targ is the name of a saved list, remove from @targ
 * any elements of @sub that it contains.
 *
 * Returns: 0 on success, non-zero code on failure.
 */

int subtract_from_list_by_name (const char *targ, const int *sub)
{
    saved_list *sl = get_saved_list_by_name(targ);
    int err = 0;

    if (sl == NULL) {
      err = E_UNKVAR;
    } else {
      int *tmp = real_gretl_list_omit(sl->list, sub, 1, 
                              LIST_OMIT_SLOPPY,
                              &err);

      if (!err) {
          free(sl->list);
          sl->list = tmp;
      }
    } 

    return err;
}

/**
 * replace_list_by_name:
 * @targ: the name of the target list.
 * @new: replacement list
 *
 * If @targ is the name of a saved list, replace the
 * list of that name with @new.
 *
 * Returns: 0 on success, non-zero code on failure.
 */

int replace_list_by_name (const char *targ, const int *new)
{
    saved_list *sl = get_saved_list_by_name(targ);
    int err = 0;

    if (sl == NULL) {
      err = E_UNKVAR;
    } else {
      int *tmp = gretl_list_copy(new);

      if (tmp == NULL) {
          err = E_ALLOC;
      } else {
          free(sl->list);
          sl->list = tmp;
      }         
    }

    return err;
}

static int real_remember_list (const int *list, const char *name, 
                         int force_new, PRN *prn)
{
    saved_list *orig = NULL;
    int err = 0;

    if (list == NULL) {
      return E_DATA;
    }

#if LDEBUG
    fprintf(stderr, "remember_list (in): name='%s', force_new=%d,"
          " n_lists=%d\n", name, force_new, n_lists);
#endif

    if (!force_new) {
      orig = get_saved_list_by_name(name);
    }

    if (orig != NULL) {
      /* replace existing list of same name */
      free(orig->list);
      orig->list = gretl_list_copy(list);
      if (orig->list == NULL) {
          err = E_ALLOC;
      } else if (gretl_messages_on() && !gretl_looping_quietly()) {
          pprintf(prn, _("Replaced list '%s'\n"), name);
      }
    } else {
      saved_list **lstack;

      err = check_varname(name);
      if (err) {
          return err;
      }

      lstack = realloc(list_stack, (n_lists + 1) * sizeof *lstack);
      if (lstack == NULL) {
          return E_ALLOC;
      }
      list_stack = lstack;

      list_stack[n_lists] = saved_list_new(list, name);
      if (list_stack[n_lists] == NULL) {
          err = E_ALLOC;
      } else {
          if (gretl_messages_on()) {
            const char *realname = list_stack[n_lists]->name;

            if (list[0] > 0) {
                pprintf(prn, _("Added list '%s'\n"), realname);
            }
            if (strlen(realname) < strlen(name)) {
                pprintf(prn, _("Warning: the name was truncated to %d characters\n"), 
                      VNAMELEN - 1);
            }
          }
          n_lists++;
      }
    }

#if LDEBUG
    fprintf(stderr, "remember_list (out): n_lists=%d, ", n_lists);
    fprintf(stderr, "list_stack[%d]=%p\n", n_lists - 1, 
          (void *) list_stack[n_lists - 1]);
#endif

    return err;
}

/**
 * remember_list:
 * @list: array of integers, the first element being a count
 * of the following elements.
 * @name: name to be given to the list.
 * @prn: printing struct.
 *
 * Adds @list to the stack of saved lists and associates it
 * with @name, unless there is already a list with the given
 * name in which case the original list is replaced.  A status
 * message is printed to @prn.
 *
 * Returns: 0 on success, non-zero code on error.
 */

int remember_list (const int *list, const char *name, PRN *prn)
{
    return real_remember_list(list, name, 0, prn);
}

static int destroy_saved_list (saved_list *sl)
{
    saved_list **lstack;
    int found = 0;
    int i, j, err = 0;

    for (i=0; i<n_lists; i++) {
      if (list_stack[i] == NULL) {
          break;
      }
      if (list_stack[i] == sl) {
          free_saved_list(sl);
          for (j=i; j<n_lists - 1; j++) {
            list_stack[j] = list_stack[j+1];
          }
          list_stack[n_lists - 1] = NULL;
          found = 1;
          break;
      } 
    }

    if (!found) {
      err = E_DATA;
    } else {
      n_lists--;
      if (n_lists == 0) {
          free(list_stack);
          list_stack = NULL;
      } else {
          lstack = realloc(list_stack, n_lists * sizeof *list_stack);
          if (lstack == NULL) {
            err = E_ALLOC;
          } else {
            list_stack = lstack;
          } 
      }
    }   

    return err;
}

/**
 * rename_saved_list:
 * @orig: the original name of the list.
 * @new: the new name to be given.
 *
 * Renames a saved list from @orig to @new.  If there is
 * already a list called @new, it is destroyed.
 *
 * Returns: 0 on success, non-zero on error.
 */

int rename_saved_list (const char *orig, const char *new)
{
    saved_list *sl0, *sl1;
    int err = 0;

    sl0 = get_saved_list_by_name(orig);
    if (sl0 == NULL) {
      err = 1;
    } else {
      /* is there already a list called @new? */
      sl1 = get_saved_list_by_name(new);
      if (sl1 != NULL) {
          err = destroy_saved_list(sl1);
      }
      *sl0->name = '\0';
      strncat(sl0->name, new, VNAMELEN - 1);
    } 

    return err;
}

/**
 * copy_named_list_as:
 * @orig: the name of the original list.
 * @new: the name to be given to the copy.
 *
 * If a saved list is found by the name @orig, a copy of
 * this list is added to the stack of saved lists under the
 * name @new.  This is intended for use when a list is given
 * as the argument to a user-defined function: it is copied
 * under the name assigned by the function's parameter list.
 *
 * Returns: 0 on success, non-zero on error.
 */

int copy_named_list_as (const char *orig, const char *new)
{
    saved_list *sl;
    int err = 0;

    sl = get_saved_list_by_name(orig);
    if (sl == NULL) {
      err = 1;
    } else {
      err = real_remember_list(sl->list, new, 1, NULL);
      if (!err) {
          sl = list_stack[n_lists - 1];
          sl->level += 1;
      }
    }

    return err;
}

/**
 * named_list_lower_level:
 * @name: the name of the list.
 *
 * If a saved list is found by the name @name, at the
 * current level of function execution, lower its level
 * by 1.  This is intended for use when a list is 
 * returned by a user-defined function: it is shifted to
 * the level of the caller.
 *
 * Returns: 0 on success, non-zero on error.
 */ 

int named_list_lower_level (const char *name)
{
    saved_list *sl;
    int err = 0;

    sl = get_saved_list_by_name(name);
    if (sl == NULL) {
      err = E_DATA;
    } else {
      sl->level -= 1;
    }

    return err;
}

/**
 * create_named_null_list:
 * @name: the name to be given to the list.
 *
 * Creates an empty list under the given @name and adds it
 * to the stack of saved lists at the next level of
 * function execution.  This is intended for use when a null 
 * list is given as an argument to a user-defined function.
 *
 * Returns: 0 on success, non-zero on error.
 */

int create_named_null_list (const char *name)
{
    saved_list *sl;
    int *list;
    int err;

    list = gretl_null_list();
    if (list == NULL) {
      return E_ALLOC;
    }

    err = real_remember_list(list, name, 1, NULL);
    if (!err) {
      sl = list_stack[n_lists - 1];
      sl->level += 1;
    } else {
      free(list);
    }

    return err;
}

/**
 * destroy_saved_lists_at_level:
 * @level: stack level of function execution.
 *
 * Destroys and removes from the stack of saved lists all
 * lists that were created at the given @level.  This is 
 * part of the cleanup that is performed when a user-defined
 * function terminates.
 *
 * Returns: 0 on success, non-zero on error.
 */

int destroy_saved_lists_at_level (int level)
{
    saved_list **lstack;
    int i, j, nl = 0;
    int err = 0;

    for (i=0; i<n_lists; i++) {
      if (list_stack[i] == NULL) {
          break;
      }
      if (list_stack[i]->level == level) {
          free_saved_list(list_stack[i]);
          for (j=i; j<n_lists - 1; j++) {
            list_stack[j] = list_stack[j+1];
          }
          list_stack[n_lists - 1] = NULL;
          i--;
      } else {
          nl++;
      }
    }

    if (nl < n_lists) {
      n_lists = nl;
      if (nl == 0) {
          free(list_stack);
          list_stack = NULL;
      } else {
          lstack = realloc(list_stack, nl * sizeof *list_stack);
          if (lstack == NULL) {
            err = E_ALLOC;
          } else {
            list_stack = lstack;
          }
      }
    }

    return err;
}

int delete_list_by_name (const char *name)
{
    saved_list *sl;

    sl = get_saved_list_by_name(name);
    if (sl == NULL) {
      return E_UNKVAR;
    } else {
      return destroy_saved_list(sl);
    }
}

static int var_is_deleted (const int *dlist, int dmin, int i)
{
    int v = dmin + i - 1;

    if (dlist != NULL) {
      return in_gretl_list(dlist, v);
    } else {
      return (v >= dmin);
    }
}

/**
 * gretl_lists_revise:
 * @dlist: list of variables to be deleted (or %NULL).
 * @dmin: lowest ID number of deleted var (referenced only
 * if @dlist is %NULL).
 *
 * Goes through any saved lists, adjusting the ID numbers
 * they contain to reflect the deletion from the dataset of
 * certain variables: those referenced in @dlist, if given, 
 * or if @dlist is %NULL, those variables with IDs greater 
 * than or equal to @dmin.
 *
 * Returns: 0 on success, non-zero code on failure.
 */

int gretl_lists_revise (const int *dlist, int dmin)
{
    int *list, *maplist;
    int lmax = 0;
    int i, j, k;

#if 0
    fprintf(stderr, "gretl_lists_revise: dlist = %p, dmin = %d\n", 
          (void *) dlist, dmin);
#endif

    if (dlist != NULL) {
      /* determine lowest deleted ID */
      dmin = dlist[1];
      for (i=2; i<=dlist[0]; i++) {
          if (dlist[i] > 0 && dlist[i] < dmin) {
            dmin = dlist[i];
          }
      }
    }

    /* find highest ID ref'd in any saved list */
    for (j=0; j<n_lists; j++) {
      list = list_stack[j]->list;
      for (i=1; i<=list[0]; i++) {
          if (list[i] > lmax) {
            lmax = list[i];
          }
      }
    }

    if (lmax < dmin) {
      /* nothing to be done */
      return 0;
    }

    /* make mapping from old to new IDs */

    maplist = gretl_list_new(lmax - dmin + 1);
    if (maplist == NULL) {
      return E_ALLOC;
    }

    j = dmin;

    for (i=1; i<=maplist[0]; i++) {
      if (var_is_deleted(dlist, dmin, i)) {
          maplist[i] = -1;
      } else {
          maplist[i] = j++;
      }
    }

    /* use mapping to revise saved lists */
    for (j=0; j<n_lists; j++) {
      list = list_stack[j]->list;
      for (i=list[0]; i>0; i--) {
          k = list[i] - dmin + 1;
          if (k >= 1) {
            if (maplist[k] == -1) {
                gretl_list_delete_at_pos(list, i);
            } else {
                list[i] = maplist[k];
            }
          }
      }
    }

    free(maplist);

    return 0;
}

/**
 * gretl_lists_cleanup:
 *
 * Frees all resources associated with the internal
 * apparatus for saving and retrieving named lists.
 */

void gretl_lists_cleanup (void)
{
    int i;

    for (i=0; i<n_lists; i++) {
      free_saved_list(list_stack[i]);
    }

    free(list_stack);
    list_stack = NULL;
    n_lists = 0;
}

/**
 * gretl_list_new:
 * @nterms: the maximum number of elements to be stored in the list.
 * 
 * Creates a newly allocated list with space for @nterms elements,
 * besides the leading element, which in a gretl list always
 * holds a count of the number of elements that follow.  This
 * leading element is initialized appropriately.  For example, if
 * @nterms = 4, space for 5 integers is allocated and the first
 * element of the array is set to 4.  The other elements of 
 * the list are initialized to 0.
 *
 * Returns: the newly allocated list, or %NULL on failure.
 */

int *gretl_list_new (int nterms)
{
    int *list = NULL;
    int i;
    
    if (nterms < 0) {
      return NULL;
    }

    list = malloc((nterms + 1) * sizeof *list);

    if (list != NULL) {
      list[0] = nterms;
      for (i=1; i<=nterms; i++) {
          list[i] = 0;
      }
    }

    return list;
}

/**
 * gretl_consecutive_list_new:
 * @lmin: starting value for consecutive list elements.
 * @lmax: ending value.
 * 
 * Creates a newly allocated list whose elements run from
 * @lmin to @lmax consecutively.
 *
 * Returns: the newly allocated list, or %NULL on failure.
 */

int *gretl_consecutive_list_new (int lmin, int lmax)
{
    int *list = NULL;
    int i, n;

    n = lmax - lmin + 1;
    if (n <= 0) {
      return NULL;
    }

    list = gretl_list_new(n);

    if (list != NULL) {
      for (i=0; i<n; i++) {
          list[i+1] = lmin + i;
      }
    }

    return list;
}

/**
 * gretl_list_resize:
 * @oldlist: pointer to list to be resized.
 * @nterms: the new maximum number of elements for the list.
 * 
 * Resizes the content of @oldlist to hold @nterms, and adjusts
 * the first element to reflect the new size.  If the new
 * list is longer than the old, the extra elements are initialized 
 * to zero.
 *
 * Returns: the resized list, or %NULL on failure.
 */

int *gretl_list_resize (int **oldlist, int nterms)
{
    int *list = NULL;
    int i, oldn = 0;

    if (nterms < 0 || oldlist == NULL) {
      return NULL;
    }

    if (*oldlist != NULL) {
      oldn = (*oldlist)[0];
      if (nterms == oldn) {
          /* no-op */
          return *oldlist;
      }
    }

    list = realloc(*oldlist, (nterms + 1) * sizeof *list);

    if (list != NULL) {
      list[0] = nterms;
      *oldlist = list;
      for (i=oldn+1; i<=list[0]; i++) {
          list[i] = 0;
      }
    } else {
      free(*oldlist);
      *oldlist = NULL;
    }

    return list;
}

/**
 * gretl_list_append_term:
 * @plist: pointer to list to be augmented.
 * @v: the term to be added.
 * 
 * Resizes (or allocates from scratch) the content of @plist,
 * so that it can hold one extra element, and sets the last
 * element to @v.
 *
 * Returns: the augmented list, or %NULL on failure.
 */

int *gretl_list_append_term (int **plist, int v)
{
    int *list = NULL;

    if (*plist == NULL) {
      list = gretl_list_new(1);
      if (list != NULL) {
          list[1] = v;
      }
    } else {
      int oldn = (*plist)[0];

      list = realloc(*plist, (oldn + 2) * sizeof *list);
      if (list != NULL) {
          list[0] += 1;
          list[list[0]] = v;
      } else {
          free(*plist);
      }
    }

    *plist = list;

    return list;
}

/**
 * gretl_list_sort:
 * @list: list to be sorted.
 * 
 * Sorts the elements from position 1 to the end of @list
 * in ascending order.
 *
 * Returns: the sorted list.
 */

int *gretl_list_sort (int *list)
{
    int i, sorted = 1;

    for (i=1; i<list[0]; i++) {
      if (list[i] > list[i+1]) {
          sorted = 0;
          break;
      }
    }

    if (!sorted) {
      qsort(list + 1, list[0], sizeof *list, gretl_compare_ints);
    }

    return list;
}

/**
 * gretl_list_cmp:
 * @list1: gretl list.
 * @list2: gretl list.
 * 
 * Returns: 0 if @list1 and @list2 have identical content,
 * otherwise 1.
 */

int gretl_list_cmp (const int *list1, const int *list2)
{
    int i;

    for (i=0; i<=list1[0]; i++) {
      if (list2[i] != list1[i]) {
          return 1;
      }
    }

    return 0;
}

/**
 * gretl_null_list:
 * 
 * Creates a newly allocated "list" with only one member, 
 * which is set to zero.
 *
 * Returns: the newly allocated list, or %NULL on failure.
 */

int *gretl_null_list (void)
{
    int *list = malloc(sizeof *list);

    if (list != NULL) {
      list[0] = 0;
    }

    return list;
}

/**
 * gretl_list_copy:
 * @src: an array of integers, the first element of which holds
 * a count of the number of elements following.
 *
 * Returns: an allocated copy @src (or %NULL if @src is %NULL).
 */

int *gretl_list_copy (const int *src)
{
    int *targ = NULL;
    int i;

    if (src != NULL) {
      targ = malloc((src[0] + 1) * sizeof *targ);
      if (targ != NULL) {
          for (i=0; i<=src[0]; i++) {
            targ[i] = src[i];
          }
      }
    }

    return targ;
}

/**
 * gretl_list_from_string:
 * @liststr: string representation of list of integers.
 *
 * Reads a string containing a list of integers, separated by
 * spaces and/or commas and possibly wrapped in parentheses,
 * and constructs an array of these integers.  The first 
 * element is the number of integers that follow.
 *
 * Returns: the allocated array, or %NULL on failure.
 */

int *gretl_list_from_string (const char *liststr)
{
    const char *s = liststr;
    char numstr[8];
    int *list;
    int n = 0;

    if (liststr == NULL) {
      return NULL;
    }

    while (*s) {
      s += strspn(s, " ,()");
      if (*s && sscanf(s, "%7[^ ,()]", numstr)) {
          n++;
          s += strlen(numstr);
      }
    }

    if (n == 0) {
      return NULL;
    }

    list = gretl_list_new(n);
    if (list == NULL) {
      return NULL;
    }

    s = liststr;
    n = 1;
    while (*s) {
      s += strspn(s, " ,()");
      if (*s && sscanf(s, "%7[^ ,()]", numstr)) {
          if (*numstr == ';') {
            list[n++] = LISTSEP;
          } else {
            list[n++] = atoi(numstr);
          }
          s += strlen(numstr);
      }
    }    

    return list;
}

/**
 * gretl_list_to_string:
 * @list: array of integers.
 * 
 * Prints the given @list of integers into a newly
 * allocated string, separated by single spaces and with
 * one leading space.  This function is designed to handle 
 * positive integers in a range that is sensible for ID 
 * numbers of variables, typically with three digits or less, 
 * and will fail if the list contains any numbers greater 
 * than 999.
 *
 * Returns: The string representation of the list on success,
 * or %NULL on failure.
 */

char *gretl_list_to_string (const int *list)
{
    char *buf;
    char numstr[8];
    int len, i, err = 0;

    len = 4 * (list[0] + 1);
    if (len > MAXLINE - 32) {
      return NULL;
    }

    buf = malloc(len);
    if (buf == NULL) {
      return NULL;
    }

    *buf = '\0';
    for (i=1; i<=list[0]; i++) {
      if (abs(list[i] > 999)) {
          err = 1;
          break;
      }
      if (list[i] == LISTSEP) {
          strcat(buf, " ;");
      } else {
          sprintf(numstr, " %d", list[i]);
          strcat(buf, numstr);
      }
    }

    if (err) {
      free(buf);
      buf = NULL;
    }

    return buf;
}

/**
 * in_gretl_list:
 * @list: an array of integers, the first element of which holds
 * a count of the number of elements following.
 * @k: integer to test.
 *
 * Checks whether @k is present among the members of @list,
 * in position 1 or higher.
 *
 * Returns: the position of @k in @list, or 0 if @k is not
 * present. 
 */

int in_gretl_list (const int *list, int k)
{
    int i, ret = 0;

    if (list != NULL) {
      for (i=1; i<=list[0] && !ret; i++) {
          if (list[i] == k) {
            ret = i;
          }
      }
    }

    return ret;
}

static void reglist_move_const (int *list, int from)
{
    int i, cnum = list[from];

    for (i=from; i>2; i--) {
      list[i] = list[i-1];
    }

    list[2] = cnum;
}

/**
 * reglist_check_for_const:
 * @list: regression list suitable for use with a gretl
 * model (should not contain #LISTSEP).
 * @Z: data array.
 * @pdinfo: dataset information.
 *
 * Checks @list for an intercept term (a variable all of
 * whose valid values in sample are 1).  If such a variable
 * is present, it is moved to position 2 in the list.
 *
 * Returns: 1 if the list contains an intercept, else 0.
 */

int reglist_check_for_const (int *list, const double **Z,
                       const DATAINFO *pdinfo)
{
    int cpos = gretl_list_const_pos(list, 2, Z, pdinfo);
    int ret = 0;

    if (cpos > 1) {
      ret = 1;
    }

    if (cpos > 2) {
      reglist_move_const(list, cpos);
    }

    return ret;
}

/**
 * gretl_list_delete_at_pos:
 * @list: an array of integers, the first element of which holds
 * a count of the number of elements following.
 * @pos: position at which to delete list element.
 *
 * Deletes the element at position @pos from @list and moves any
 * remaining elements forward.  Decrements the value of the first,
 * counter, element of @list.
 *
 * Returns: 0 on success, 1 on error.
 */

int gretl_list_delete_at_pos (int *list, int pos)
{
    int i, err = 0;

    if (pos < 1 || pos > list[0]) {
      err = 1;
    } else {
      for (i=pos; i<list[0]; i++) {
          list[i] = list[i + 1];
      }

      list[list[0]] = 0;
      list[0] -= 1;
    }

    return err;
}

/**
 * gretl_list_purge_const:
 * @list: list of variable ID numbers.
 * @Z: data array.
 * @pdinfo: dataset information.
 *
 * Checks @list from position 1 onward for the presence of a 
 * variable whose valid values in sample all equal 1.0.  If 
 * such a variable is found, it is deleted from @list (that is, 
 * any following elements are moved forward by one and list[0] 
 * is decremented by 1).
 *
 * Returns: 1 if a constant was found and deleted, else 0.
 */

int gretl_list_purge_const (int *list, const double **Z,
                      const DATAINFO *pdinfo)
{
    int i, gotc = 0;
    int l0 = list[0];

    /* handle the case where the constant comes last; if it's
       the only element behind the list separator, remove both
       the constant and the separator */

    if (list[l0] == 0 || true_const(list[l0], Z, pdinfo)) {
      gotc = 1;
      list[0] -= 1;
      if (list[l0 - 1] == LISTSEP) {
          list[l0 - 1] = 0;
          list[0] -= 1;
      }
    } else {
      for (i=1; i<l0; i++) {
          if (list[i] == 0 || true_const(list[i], Z, pdinfo)) {
            for ( ; i<l0; i++) {
                list[i] = list[i+1];
            }
            list[l0] = 0;
            list[0] -= 1;
            gotc = 1;
            break;
          }
      }
    }

    return gotc;
}

static int *real_gretl_list_union (const int *orig, const int *add, 
                           int *err, int duperr)
{
    int i, j, k;
    int *big;
    const int norig = orig[0];
    const int nadd = add[0];

    *err = 0;

    big = gretl_list_new(norig + nadd);
    if (big == NULL) {
      *err = E_ALLOC;
      return NULL;
    }

    for (i=0; i<=norig; i++) {
      big[i] = orig[i];
    }

    k = orig[0];

    for (i=1; i<=nadd; i++) {
      int match = 0;

      for (j=1; j<=norig; j++) {
          if (add[i] == orig[j]) {
            /* a "new" var was already present */
            if (duperr) {
                free(big);
                *err = E_ADDDUP;
                return NULL;
            } else {
                match = 1;
            }
          }
      }
      if (!match) {
          big[0] += 1;
          big[++k] = add[i];
      }
    }

    if (duperr && big[0] == norig) {
      free(big);
      *err = E_NOADD;
      return NULL;
    }

    return big;
}

/**
 * gretl_list_add:
 * @orig: an array of integers, the first element of which holds
 * a count of the number of elements following.
 * @add: list of variables to be added.
 * @err: location to receive error code.
 *
 * Creates a list containing the union of elements of @orig 
 * and the elements of @add.  If one or more elements of
 * @add were already present in @orig, the error code is
 * %E_ADDDUP.
 *
 * Returns: new list on success, %NULL on error.
 */

int *gretl_list_add (const int *orig, const int *add, int *err)
{
    return real_gretl_list_union(orig, add, err, 1);
}

/**
 * gretl_list_union:
 * @l1: list of integers.
 * @l2: list of integers.
 * @err: location to receive error code.
 *
 * Creates a list holding the union of @l1 and @l2.
 *
 * Returns: new list on success, %NULL on error.
 */

int *gretl_list_union (const int *l1, const int *l2, int *err)
{
    return real_gretl_list_union(l1, l2, err, 0);
}

/**
 * gretl_list_intersection:
 * @l1: list of integers.
 * @l2: list of integers.
 * @err: location to receive error code.
 *
 * Creates a list holding the intersection of @l1 and @l2.
 *
 * Returns: new list on success, %NULL on error.
 */

int *gretl_list_intersection (const int *l1, const int *l2, int *err)
{
    int *ret = NULL;
    int i, j;
    int n = 0;

    for (i=1; i<=l1[0]; i++) {
      for (j=1; j<=l2[0]; j++) {
          if (l2[j] == l1[i]) {
            n++;
            break;
          }
      }
    }

    if (n == 0) {
      ret = gretl_null_list();
    } else {
      ret = gretl_list_new(n);
      if (ret != NULL) {
          n = 1;
          for (i=1; i<=l1[0]; i++) {
            for (j=1; j<=l2[0]; j++) {
                if (l2[j] == l1[i]) {
                  ret[n++] = l1[i];
                  break;
                }
            }
          }
      }
    }

    if (ret == NULL) {
      *err = E_ALLOC;
    }

    return ret;
}

/**
 * gretl_list_omit_last:
 * @orig: an array of integers, the first element of which holds
 * a count of the number of elements following.
 * @err: location to receive error code.
 *
 * Creates a list containing all but the last element of @orig.
 *
 * Returns: new list on success, %NULL on error.
 */

int *gretl_list_omit_last (const int *orig, int *err)
{
    int *list = NULL;
    int i;

    *err = 0;

    if (orig[0] < 2) {
      *err = E_NOVARS;
    }

    /* can't handle compound lists */
    if (*err == 0) {
      for (i=1; i<=orig[0]; i++) {
          if (orig[i] == LISTSEP) {
            *err = 1;
            break;
          }
      }
    }

    if (*err == 0) {
      list = malloc(orig[0] * sizeof *list);
      if (list == NULL) {
         *err = E_ALLOC;
      } 
    }
    
    if (list != NULL) {
      list[0] = orig[0] - 1;
      for (i=1; i<orig[0]; i++) {
          list[i] = orig[i];
      }
    }

    return list;
}

static int list_count (const int *list)
{
    int i, k = 0;

    for (i=1; i<=list[0]; i++) {
      if (list[i] == LISTSEP) {
          break;
      } else {
          k++;
      }
    }

    return k;
}

static int *real_gretl_list_omit (const int *orig, const int *omit, 
                          int minpos, int mode, int *err)
{
    const int nomit = omit[0];
    const int norig = list_count(orig);
    int real_nomit = nomit;
    int *smal = NULL;
    int i, j, k;

    *err = 0;

    /* check for spurious "omissions" */
    for (i=1; i<=nomit; i++) {
      int pos = in_gretl_list(orig, omit[i]);

      if (pos < minpos) {
          if (mode == LIST_OMIT_TIGHT) {
            sprintf(gretl_errmsg, _("Variable %d was not in the original list"),
                  omit[i]);
            *err = 1;
            return NULL;
          } else {
            real_nomit--;
          }
      }
    }

    if (minpos > 1) {
      /* it's an error to attempt to omit all vars */
      if (nomit == norig - 1) {
          *err = E_NOVARS;
          return NULL;
      }
    }

    if (real_nomit == norig) {
      /* omitting all */
      smal = gretl_null_list();
      if (smal == NULL) {
          *err = E_ALLOC;
      }
      return smal;
    }

    smal = gretl_list_new(norig - real_nomit);
    if (smal == NULL) {
      *err = E_ALLOC;
      return NULL;
    }

    for (i=1; i<minpos; i++) {
      /* copy unaltered portion */
      smal[i] = orig[i];
    }

    k = minpos;
    for (i=minpos; i<=norig; i++) {
        int match = 0;

        for (j=1; j<=nomit; j++) {
            if (orig[i] == omit[j]) {
                match = 1; /* matching var: omit it */
            break;
            }
        }
        if (!match) { /* var is not in omit list: keep it */
            smal[k++] = orig[i];
        }
    }

    return smal;
}

/**
 * gretl_list_omit:
 * @orig: an array of integers, the first element of which holds
 * a count of the number of elements following.
 * @omit: list of variables to drop.
 * @minpos: minimum position to check.  This should be 2 for a regular
 * regression list, to skip the dependent var in position 1; but in
 * other contexts it may be 1 to start from the first element of @orig.
 * @err: pointer to receive error code.
 *
 * Creates a list containing the elements of @orig that are not
 * present in @omit.
 *
 * Returns: new list on success, %NULL on error.
 */

int *gretl_list_omit (const int *orig, const int *omit, int minpos, int *err)
{
    return real_gretl_list_omit(orig, omit, minpos, LIST_OMIT_TIGHT, err);
}

/**
 * gretl_list_diff:
 * @targ: target list (must be pre-allocated).
 * @biglist: inclusive list.
 * @sublist: subset of biglist.
 *
 * Fills out @targ with the elements of @biglist, from position 2 
 * onwards, that are not present in @sublist.  It is assumed that 
 * the variable ID number in position 1 (dependent variable) is the 
 * same in both lists.  It is an error if, from position 2 on, 
 * @sublist is not a proper subset of @biglist.  See also 
 * #gretl_list_diff_new.
 *
 * Returns: 0 on success, 1 on error.
 */

int gretl_list_diff (int *targ, const int *biglist, const int *sublist)
{
    int i, j, k, n;
    int match, err = 0;

    n = biglist[0] - sublist[0];
    targ[0] = n;

    if (n <= 0) {
      err = 1;
    } else {
      k = 1;
      for (i=2; i<=biglist[0]; i++) {
          match = 0;
          for (j=2; j<=sublist[0]; j++) {
            if (sublist[j] == biglist[i]) {
                match = 1;
                break;
            }
          }
          if (!match) {
            if (k <= n) {
                targ[k++] = biglist[i];
            } else {
                err = 1;
            }
          }
      }
    }

    return err;
}

/**
 * gretl_list_diff_new:
 * @biglist: inclusive list.
 * @sublist: subset of biglist.
 * @minpos: position in lists at which to start.
 *
 * Returns: a newly allocated list including the elements of @biglist,
 * from position @minpos onwards, that are not present in @sublist, 
 * again from @minpos onwards, or %NULL on failure.  
 */

int *gretl_list_diff_new (const int *biglist, const int *sublist,
                    int minpos)
{
    int *targ = NULL;
    int i, j, bi;
    int match;

    if (biglist == NULL || sublist == NULL) {
      return NULL;
    }

    targ = gretl_null_list();
    if (targ == NULL) {
      return NULL;
    }

    for (i=minpos; i<=biglist[0]; i++) {
      bi = biglist[i];
      match = 0;
      for (j=minpos; j<=sublist[0]; j++) {
          if (sublist[j] == bi) {
            match = 1;
            break;
          }
      }
      if (!match) {
          /* but is this var already accounted for? */
          for (j=1; j<=targ[0]; j++) {
            if (targ[j] == bi) {
                match = 1;
                break;
            }
          }
      }
      if (!match) {
          targ = gretl_list_append_term(&targ, biglist[i]);
          if (targ == NULL) {
            break;
          }
      }
    }

    return targ;
}

/**
 * gretl_list_add_list:
 * @targ: location of list to which @src should be added.
 * @src: list to be added to @targ.
 *
 * Adds @src onto the end of @targ.  The length of @targ becomes the
 * sum of the lengths of the two original lists.
 *
 * Returns: 0 on success, non-zero on failure.
 */

int gretl_list_add_list (int **targ, const int *src)
{
    int *big;
    int n1 = (*targ)[0];
    int n2 = src[0];
    int i, err = 0;

    if (targ == NULL || *targ == NULL) {
      return E_DATA;
    }

    if (src == NULL || *src == 0) {
      /* no-op */
      return 0;
    }

    big = realloc(*targ, (n1 + n2 + 1) * sizeof *big);

    if (big == NULL) {
      err = E_ALLOC;
    } else {
      big[0] = n1 + n2;
      for (i=1; i<=src[0]; i++) {
          big[n1 + i] = src[i];
      }
      *targ = big;
    }

    return err;
}

/**
 * gretl_list_insert_list:
 * @targ: location of list into which @src should be inserted.
 * @src: list to be inserted.
 * @pos: zero-based position at which @src should be inserted.
 *
 * Inserts @src into @targ at @pos.  The length of @targ becomes the
 * sum of the lengths of the two original lists.
 *
 * Returns: 0 on success, non-zero on failure.
 */

int gretl_list_insert_list (int **targ, const int *src, int pos)
{
    int *big;
    int n1 = (*targ)[0];
    int n2 = src[0];
    int bign = n1 + n2;
    int i, err = 0;

    if (pos > n1 + 1) {
      return 1;
    }

    big = realloc(*targ, (bign + 1) * sizeof *big);
    if (big == NULL) {
      err = E_ALLOC;
    } else {
      big[0] = bign;
      for (i=bign; i>=pos+n2; i--) {
          big[i] = big[i-n2];
      }
      for (i=1; i<=src[0]; i++) {
          big[pos+i-1] = src[i];
      }
      *targ = big;
    }

    return err;
}

/**
 * gretl_list_insert_list_minus:
 * @targ: location of list into which @src should be inserted.
 * @src: list to be inserted.
 * @pos: zero-based position at which @src should be inserted.
 *
 * Inserts @src into @targ at @pos.  The length of @targ becomes the
 * sum of the lengths of the two original lists minus one.  This
 * can be useful if we were expecting to insert a single variable
 * but found we had to insert a list instead.  Insertion of @src
 * overwrites any entries in @targ beyond @pos (the expectation is
 * that this function will be called in the process of assembling
 * @targ, in left-to-right mode).
 *
 * Returns: 0 on success, non-zero on failure.
 */

int gretl_list_insert_list_minus (int **targ, const int *src, int pos)
{
    int *big;
    int n1 = (*targ)[0];
    int n2 = src[0];
    int bign = n1 - 1 + n2;
    int i, err = 0;

    if (pos > n1 + 1) {
      return 1;
    }

    big = realloc(*targ, (bign + 1) * sizeof *big);
    if (big == NULL) {
      err = E_ALLOC;
    } else {
      big[0] = bign;
      for (i=1; i<=src[0]; i++) {
          big[pos+i-1] = src[i];
      }
      *targ = big;
    }

    return err;
}

/**
 * list_members_replaced:
 * @list: an array of integer variable ID numbers, the first element
 * of which holds a count of the number of elements following.
 * @pdinfo: dataset information.
 * @ref_id: ID number of reference #MODEL.
 *
 * Checks whether any variable in @list has been redefined via
 * gretl's %genr command since a previous model (identified by
 * @ref_id) was estimated.
 *
 * Returns: 1 if any variables have been replaced, 0 otherwise.
 */

int list_members_replaced (const int *list, const DATAINFO *pdinfo,
                     int ref_id)
{
    const char *errmsg = N_("Can't do this: some vars in original "
                      "model have been redefined");
    const char *label;
    char rword[16];
    int j, mc, repl, err = 0;

    if (ref_id == 0) {
      mc = get_model_count();
    } else {
      mc = ref_id;
    }

    for (j=1; j<=list[0]; j++) {
      if (list[j] == LISTSEP) {
          continue;
      }
      label = VARLABEL(pdinfo, list[j]);
      *rword = '\0';
      sscanf(label, "%15s", rword);
      if (!strcmp(rword, _("Replaced"))) {
          repl = 0;
          sscanf(label, "%*s %*s %*s %d", &repl);
          if (repl >= mc) {
            strcpy(gretl_errmsg, _(errmsg));
            err = E_DATA;
            break;
          }
      }
    }

    return err;
}

/**
 * gretl_list_const_pos:
 * @list: an array of integer variable ID numbers, the first element
 * of which holds a count of the number of elements following.
 * @minpos: position in @list at which to start the search (>= 1).
 *
 * Checks @list for the presence, in position @minpos or higher, of
 * a variable whose valid values in sample all equal 1.  This usually
 * amounts to checking whether a list of regressors includes
 * an intercept term.
 * 
 * Returns: The list position of the const, or 0 if none is
 * found.
 */

int gretl_list_const_pos (const int *list, int minpos, const double **Z, 
                    const DATAINFO *pdinfo)
{
    int i;

    if (minpos < 1) {
      return 0;
    }

    /* we give preference to the "official" const... */
    for (i=minpos; i<=list[0]; i++) {
        if (list[i] == 0) {
          return i;
      }
    }

    /* ... but if it's not found */
    for (i=minpos; i<=list[0]; i++) {
        if (true_const(list[i], Z, pdinfo)) {
          return i;
      }
    }

    return 0;
}

/**
 * gretl_list_separator_position:
 * @list: an array of integer variable ID numbers, the first element
 * of which holds a count of the number of elements following.
 *
 * Returns: if @list contains the separator for compound
 * lists, #LISTSEP, the position in @list at which this is found,
 * else 0.  The search begins at position 1.
 */

int gretl_list_separator_position (const int *list)
{
    int i;

    for (i=1; i<=list[0]; i++) {
        if (list[i] == LISTSEP) {
          return i;
      }
    }

    return 0;
}

/**
 * gretl_list_has_separator:
 * @list: an array of integer variable ID numbers, the first element
 * of which holds a count of the number of elements following.
 *
 * Returns: 1 if @list contains the separator for compound
 * lists, #LISTSEP, else 0.  The search begins at position 1.
 */

int gretl_list_has_separator (const int *list)
{
    return gretl_list_separator_position(list) > 0;
}

/**
 * gretl_list_split_on_separator:
 * @list: source list.
 * @plist1: pointer to accept first sub-list.
 * @plist2: pointer to accept second sub-list.
 *
 * If @list contains the list separator, #LISTSEP, creates two
 * sub-lists, one containing the elements of @list preceding
 * the separator and one containing the elements following
 * the separator.  The sub-lists are newly allocated, and assigned
 * as the content of @plist1 and @plist2 respectively.
 *
 * Returns: 0 on success, %E_ALLOC is memory allocation fails,
 * or %E_DATA if @list does not contain a separator.
 */

int gretl_list_split_on_separator (const int *list, int **plist1, int **plist2)
{
    int *list1 = NULL, *list2 = NULL;
    int i, n = 0;
    int err = 0;

    for (i=1; i<=list[0] && n==0; i++) {
      if (list[i] == LISTSEP) {
          n = i;
      }
    }

    if (n == 0) {
      err = E_PARSE;
    }

    if (n > 1) {
      list1 = gretl_list_new(n - 1);
      if (list1 == NULL) {
          return E_ALLOC;
      }
      for (i=1; i<n; i++) {
          list1[i] = list[i];
      }
    }

    if (n < list[0]) {
      list2 = gretl_list_new(list[0] - n);
      if (list2 == NULL) {
          free(list1);
          return E_ALLOC;
      }

      for (i=1; i<=list2[0]; i++) {
          list2[i] = list[i + n];
      }
    }

    *plist1 = list1;
    *plist2 = list2;
    
    return err;
}

static int real_list_dup (const int *list, int start, int stop)
{
    int i, j, ret = -1;

    for (i=start; i<stop && ret<0; i++) {
      for (j=i+1; j<=stop && ret<0; j++) {
          if (list[i] == list[j]) {
            ret = list[i];
          }
      }
    }

    return ret;
}

/**
 * gretl_list_duplicates:
 * @list: an array of integer variable ID numbers, the first element
 * of which holds a count of the number of elements following.
 * @ci: index of gretl command (for context).
 *
 * Checks whether or not a gretl list contains duplicated elements.
 * Exactly what counts as duplication depends on the context of the
 * command in which @list will be used, which is given by @ci.
 *
 * Returns: the ID number of the first duplicated variable found,
 * or -1 in case of no duplication.
 */

int gretl_list_duplicates (const int *list, GretlCmdIndex ci)
{
    int multi = 0;
    int start = 2;
    int i, ret = -1;

    if (ci == COINT) {
      start = 1;
    } else if (ci == ARCH) {
      start = 3;
    } else if (ci == ARMA) {
      for (i=list[0]-1; i>2; i--) {
          if (list[i] == LISTSEP) {
            start = i+1;
            break;
          }
      }
    } else if (ci == LAGS && list[0] > 1 && list[2] == LISTSEP) {
      start = 3;
    } else if (ci == AR || ci == SCATTERS || ci == MPOLS || ci == GARCH) {
      for (i=2; i<list[0]; i++) {
          if (list[i] == LISTSEP) {
            start = i+1;
            break;
          }
      }
    } else if (ci == TSLS || ci == HECKIT || ci == EQUATION) {
      multi = 1;
      for (i=2; i<list[0]; i++) {
          if (list[i] == LISTSEP) {
            start = i+1;
            break;
          }
      }
      ret = real_list_dup(list, start, list[0]);
      if (ret == -1) {
          ret = real_list_dup(list, 2, start - 2);
      }
    } else if (ci == VAR || ci == VECM || ci == COINT2) {
      multi = 1;
      for (i=1; i<list[0]; i++) {
          if (list[i] == LISTSEP) {
            start = i+1;
            break;
          }
      }
      ret = real_list_dup(list, start, list[0]);
      if (ret == -1) {
          ret = real_list_dup(list, 1, start - 2);
      }
    } else if (ci == ARBOND) {
      int stop = 0;

      multi = 1;
      for (i=2; i<list[0]; i++) {
          if (list[i] == LISTSEP) {
            start = i;
            break;
          }
      }
      for (i=list[0]-1; i>=2; i--) {
          if (list[i] == LISTSEP) {
            stop = i;
            break;
          }
      }

      if (stop == start) {
          ret = real_list_dup(list, start + 1, list[0]);
      } else {
          ret = real_list_dup(list, start + 1, stop - 1);
          if (ret == -1) {
            ret = real_list_dup(list, stop + 1, list[0]);
          }
      }
      multi = 1;
    } 

    if (!multi) {
      ret = real_list_dup(list, start, list[0]);
    }

    return ret;
}

/**
 * gretl_lists_share_members:
 * @list1: 
 * @list2: 
 *
 * Returns: 1 if there are any elements in common between @list1
 * and @list2, otherwise 0.
 */

int gretl_lists_share_members (const int *list1, const int *list2)
{
    int i;

    if (list1 == NULL || list2 == NULL) {
      return 0;
    }

    for (i=1; i<=list1[0]; i++) {
      if (in_gretl_list(list2, list1[i])) {
          return 1;
      }
    }

    return 0;
}

/**
 * full_var_list:
 * @pdinfo: dataset information.
 * @nvars: location for return of number of elements in full list.
 *
 * Creates a newly allocated list including all variables in the
 * dataset that are not scalars, are not hidden variables, and
 * are accessible at the current level of function execution.
 * The return value is %NULL in case either (a) allocation of
 * memory failed, or (b) the resulting list would be empty.
 * The caller can distinguish between these possibilities by
 * examining the value returned in @nvars, which will be zero if
 * and only if the resulting list would be empty.  If this is
 * not of interest to the caller, @nvars may be given as %NULL.
 *
 * Returns: the allocated list, or %NULL.
 */

int *full_var_list (const DATAINFO *pdinfo, int *nvars)
{
    int fsd = gretl_function_depth();
    int i, j, nv = 0;
    int *list = NULL;

    for (i=1; i<pdinfo->v; i++) {
      if (!var_is_hidden(pdinfo, i) &&
          STACK_LEVEL(pdinfo, i) == fsd) {
          nv++;
      }
    }

    if (nvars != NULL) {
      *nvars = nv;
    }
    
    if (nv > 0) {
      list = gretl_list_new(nv);
    }

    if (list != NULL) {
      j = 1;
      for (i=1; i<pdinfo->v; i++) {
          if (!var_is_hidden(pdinfo, i) &&
            STACK_LEVEL(pdinfo, i) == fsd) {
            list[j++] = i;
          }
      }
    }     

    return list;
}

/**
 * gretl_list_position:
 * @v: ID number of variable to find.
 * @list: list to search.
 *
 * Scans @list, from position 1 onward, for variable @v.
 * In case the list contains a list separator, #LISTSEP,
 * only the portion prior to the separator is considered.
 *
 * Returns: the 0-based position, or 0 if the variable is 
 * not found.
 */

int gretl_list_position (int v, const int *list)
{
    int i, lmax = list[0];

    /* handle lists with separator: search only first part */
    for (i=1; i<=list[0]; i++) {
      if (list[i] == LISTSEP) {
          lmax = i - 1;
          break;
      }
    }
          
    for (i=lmax; i>=1; i--) {
      if (v == list[i]) return i;
    }

    return 0;
}

/**
 * gretl_list_is_consecutive:
 * @list: list to check.
 *
 * Returns: 1 if the elements of @list, from position 1 onward,
 * are consecutive integer values, else 0.
 */

int gretl_list_is_consecutive (const int *list)
{
    int i, ret = 1;

    for (i=2; i<=list[0]; i++) {
      if (list[i] != list[i-1] + 1) {
          ret = 0;
          break;
      }
    }

    return ret;
}

/**
 * gretl_list_build:
 * @s: string list specification.
 * @pdinfo: dataset information.
 * @err: location to receive error code
 *
 * Builds a list based on the specification in @s, which may include
 * the ID numbers of variables, the names of variables, and/or the
 * names of previously defined lists (all separated by spaces).
 *
 * Returns: the constructed list, or %NULL on failure.
 */

int *gretl_list_build (const char *s, const DATAINFO *pdinfo, int *err)
{
    char test[32];
    int *list = NULL;
    int *nlist;
    int i, v, len, nf;

    list = gretl_null_list();
    if (list == NULL) {
      *err = E_ALLOC;
      return NULL;
    }

    nf = count_fields(s);
    
    for (i=0; i<nf && !*err; i++) {
      s += strspn(s, " ");
      len = strcspn(s, " ");
      if (len > 31) {
          *err = E_PARSE;
      } else {
          *test = 0;
          strncat(test, s, len);

          /* valid elements: integers, varnames, named lists */

          if (isdigit(*test)) {
            v = positive_int_from_string(test);
            if (v >= 0) {
                list = gretl_list_append_term(&list, v);
            } else {
                *err = E_PARSE;
            }
          } else {
            v = series_index(pdinfo, test);
            if (v < pdinfo->v) {
                list = gretl_list_append_term(&list, v);
            } else {
                nlist = get_list_by_name(test);
                if (nlist != NULL) {
                  *err = gretl_list_add_list(&list, nlist);
                } else {
                  *err = E_UNKVAR;
                }
            }
          }

          if (list == NULL) {
            *err = E_ALLOC;
          }
      }
      s += len;
    }

    if (*err) {
      free(list);
      list = NULL;
    }

    return list;
}

int load_user_lists_file (const char *fname)
{
    xmlDocPtr doc = NULL;
    xmlNodePtr node = NULL;
    int i, nl, err = 0;

    xmlKeepBlanksDefault(0);

    err = gretl_xml_open_doc_root(fname, "gretl-lists", &doc, &node);
    if (err) {
      return err;
    }

    if (!gretl_xml_get_prop_as_int(node, "count", &nl)) {
      err = E_DATA;
    } else if (nl <= 0) {
      err = E_DATA;
    }

    if (!err) {
      list_stack = malloc(nl * sizeof *list_stack);
      if (list_stack == NULL) {
          err = E_ALLOC;
      } else {
          n_lists = nl;
          for (i=0; i<nl; i++) {
            list_stack[i] = NULL;
          }
          for (i=0; i<nl && !err; i++) {
            list_stack[i] = malloc(sizeof **list_stack);
            if (list_stack[i] == NULL) {
                err = E_ALLOC;
            } else {
                list_stack[i]->name[0] = '\0';
                list_stack[i]->list = NULL;
                list_stack[i]->level = 0;
            }
          }
      }
    }

    if (!err) {
      xmlNodePtr cur = node->xmlChildrenNode;
      char *lname;

      i = 0;
      while (cur != NULL && !err) {
          if (!xmlStrcmp(cur->name, (XUC) "list")) {
            if (!gretl_xml_get_prop_as_string(cur, "name", &lname)) {
                err = E_DATA;
            } else {
                strncat(list_stack[i]->name, lname, VNAMELEN - 1);
                free(lname);
                list_stack[i]->list = 
                  gretl_xml_node_get_list(cur, doc, &err);
                i++;
            }
          }
          cur = cur->next;
      }
    }

    if (err && list_stack != NULL) {
      gretl_lists_cleanup();
    }

    if (doc != NULL) {
      xmlFreeDoc(doc);
      xmlCleanupParser();
    }

    return err;
}

/**
 * gretl_serialize_lists:
 * @fname: name of file to which output should be written.
 *
 * Prints an XML representation of the current saved lists,
 * if any.
 *
 * Returns: 0 on success, or if there are no saved lists, 
 * non-zero code on error.
 */

int gretl_serialize_lists (const char *fname)
{
    FILE *fp;
    int i;

    if (n_lists == 0) {
      return 0;
    }

    fp = gretl_fopen(fname, "w");
    if (fp == NULL) {
      return E_FOPEN;
    }

    gretl_xml_header(fp); 

    fprintf(fp, "<gretl-lists count=\"%d\">\n", n_lists);

    for (i=0; i<n_lists; i++) {
      gretl_xml_put_named_list(list_stack[i]->name, 
                         list_stack[i]->list, 
                         fp);
    }

    fputs("</gretl-lists>\n", fp);

    fclose(fp);

    return 0;
}

/**
 * gretl_list_print:
 * @lname: name of list.
 * @pdinfo:
 * @prn:
 * 
 * Prints to @prn the given @list of variables, by name.
 */

void gretl_list_print (const char *lname, const DATAINFO *pdinfo,
                   PRN *prn)
{
    const int *list = get_list_by_name(lname);
    int testlen = 62;
    int i, li, len = 0;

    if (list == NULL) {
      pprintf(prn, _("Unknown variable '%s'"), lname);
      pputc(prn, '\n');
    } else if (list[0] == 0) {
      pputs(prn, "null\n");
    } else {
      for (i=1; i<=list[0]; i++) {
          li = list[i];
          if (li == LISTSEP) {
            len += pputs(prn, "; ");
          } else if (li < 0 || li >= pdinfo->v) {
            len += pputs(prn, "?? ");
          } else {
            len += pprintf(prn, "%s ", pdinfo->varname[li]);
            if (len > testlen && i < list[0]) {
                pputs(prn, "\\\n "); 
                len = 1;
            }
          }
      }
      pputc(prn, '\n');
    }
}

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