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GAP 4.8.9 installation with standard packages -- copy to your CoCalc project to get it

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

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**

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*A  class1_eliminate.c          ANUPQ source                   Eamonn O'Brien

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**

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*Y  Copyright 1995-2001,  Lehrstuhl D fuer Mathematik,  RWTH Aachen,  Germany

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*Y  Copyright 1995-2001,  School of Mathematical Sciences, ANU,     Australia

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**

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*/

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#include "pq_defs.h"

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#include "pcp_vars.h"

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#include "pq_functions.h"

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/* eliminate all redundant generators to construct the consistent

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   power commutator presentation for the class 1 quotient;

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   this procedure is called only for class 1 in order to

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   eliminate redundancies brought about by collecting and

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   then echelonising words against an existing consistent

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   class 1 presentation;

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   in all other circumstances, the usual eliminate procedure

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   is called */

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void class1_eliminate(struct pcp_vars *pcp)

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{

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   register int *y = y_address;

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   register int i;

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   register int j;

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   register int k;

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   register int p1;

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   register int ba;

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   register int lg;

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   register int bound;

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   register int structure = pcp->structure;

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   register int current_class = pcp->cc;

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   register int lused = pcp->lused;

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   register int dgen = pcp->dgen;

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   register int ndgen = pcp->ndgen;

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   /* calculate new values for irredundant generators and set them up

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      in a renumbering table of length pcp->lastg - pcp->ccbeg + 1

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      which looks to compact like a normal exponent-generator string

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      pointed to by y[dgen] */

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   structure = pcp->structure;

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   lused = pcp->lused;

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   y[lused + 1] = dgen;

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   y[dgen] = -(lused + 1);

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   y[lused + 2] = pcp->lastg - pcp->ccbeg + 1;

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   ba = lused + 3 - pcp->ccbeg;

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   pcp->lused += pcp->lastg - pcp->ccbeg + 3;

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   lused = pcp->lused;

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   lg = pcp->ccbeg - 1;

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   for (i = pcp->ccbeg, bound = pcp->lastg; i <= bound; i++) {

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      y[ba + i] = 0;

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      if (y[structure + i] > 0)

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         y[ba + i] = ++lg;

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   }

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   /* update the redundant defining generators and inverses */

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   for (i = 1; i <= ndgen; i++) {

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      update(dgen + i, pcp);

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      if (pcp->overflow)

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         return;

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      update(dgen - i, pcp);

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      if (pcp->overflow)

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         return;

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   }

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   /* finally update and move structure information */

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   pcp->ppcomm = pcp->structure;

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   pcp->ppower = pcp->ppcomm;

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   k = pcp->ppower;

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   structure = pcp->structure;

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   for (i = pcp->lastg; i >= pcp->ccbeg; i--) {

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      if ((j = y[structure + i]) > 0) {

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         y[k] = j;

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         k--;

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      } else if (j < 0) {

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         /* deallocate equation for redundant generator i */

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         p1 = -j;

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         y[p1] = 0;

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      }

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   }

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   for (; i > 0; i--)

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      y[k--] = y[structure + i];

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   if (pcp->subgrp != structure)

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      delete_tables(0, pcp);

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   pcp->structure = k;

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   structure = pcp->structure;

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   pcp->words = k;

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   pcp->subgrp = k;

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   pcp->submlg = pcp->subgrp - lg;

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   pcp->lastg = lg;

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   y[pcp->clend + current_class] = pcp->lastg;

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   /* deallocate the renumbering table */

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   p1 = -y[dgen];

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   y[p1] = 0;

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   return;

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}

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