delete_tables.c

/****************************************************************************
**
*A  delete_tables.c             ANUPQ source                   Eamonn O'Brien
**
*Y  Copyright 1995-2001,  Lehrstuhl D fuer Mathematik,  RWTH Aachen,  Germany
*Y  Copyright 1995-2001,  School of Mathematical Sciences, ANU,     Australia
**
*/

#include "pq_defs.h"
#include "pcp_vars.h"

/* subroutine to delete all word and subgroup tables
   entries, depending upon the value of type;
   if type = 1 delete only the word table entries;
   if type = 2, delete only the subgroup table entries;
   if type = 0, delete both */

void delete_tables(int type, struct pcp_vars *pcp)
{
   register int *y = y_address;

   register int i;
   register int j;
   register int n;
   register int p1;
   register int nsubgp = pcp->nsubgp;
   register int address;

   /* delete all entries (pointers) in the words table */
   if (type != 2) {
      if ((n = pcp->nwords) != 0) {
         address = pcp->words;
         for (i = 1; i <= n; i++)
            if ((p1 = -y[address + i]) != 0)
               y[p1] = 0;

         /* shift up the subgroup table, if it exists */
         if (type && pcp->nsubgp) {
            j = pcp->structure + 1;
            for (i = 1; i <= nsubgp; i++, j--) {
               p1 = y[j - n];
               y[j] = p1;
               if (p1 != 0)
                  y[-p1] = j;
            }
            pcp->subgrp = j - 1;
            pcp->submlg = pcp->subgrp - pcp->lastg;
         }
         pcp->words = pcp->structure;
         pcp->nwords = 0;
      }
   }

   /* delete all entries (pointers) in the subgroup table */
   if (type != 1) {
      address = pcp->subgrp;
      for (i = 1; i <= nsubgp; i++) {
         if ((p1 = -y[address + i]) != 0) {
            y[address + i] = 0;
            y[p1] = 0;
         }
      }
      pcp->nsubgp = 0;
      pcp->subgrp = pcp->words;
      pcp->submlg = pcp->subgrp - pcp->lastg;
   }
}