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236 lines
6.5 KiB
C
236 lines
6.5 KiB
C
/* Closures for Bison
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Copyright (C) 1984, 1989, 2000-2002, 2004-2005, 2007, 2009-2015,
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2018-2020 Free Software Foundation, Inc.
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This file is part of Bison, the GNU Compiler Compiler.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include <config.h>
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#include "system.h"
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#include <bitset.h>
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#include <bitsetv.h>
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#include "closure.h"
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#include "derives.h"
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#include "getargs.h"
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#include "gram.h"
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#include "reader.h"
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#include "symtab.h"
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/* NITEMSET is the size of the array ITEMSET. */
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item_number *itemset;
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size_t nitemset;
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/* RULESET contains a bit for each rule. CLOSURE sets the bits for
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all rules which could potentially describe the next input to be
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read. */
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static bitset ruleset;
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/* internal data. See comments before set_fderives and set_firsts. */
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static bitsetv fderives = NULL;
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static bitsetv firsts = NULL;
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/* Retrieve the FDERIVES/FIRSTS sets of the nonterminals numbered Var. */
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#define FDERIVES(Var) fderives[(Var) - ntokens]
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#define FIRSTS(Var) firsts[(Var) - ntokens]
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/*-----------------.
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| Debugging code. |
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`-----------------*/
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static void
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closure_print (char const *title, item_number const *array, size_t size)
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{
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fprintf (stderr, "Closure: %s\n", title);
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for (size_t i = 0; i < size; ++i)
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{
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fprintf (stderr, " %2d: .", array[i]);
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item_number *rp;
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for (rp = &ritem[array[i]]; *rp >= 0; ++rp)
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fprintf (stderr, " %s", symbols[*rp]->tag);
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fprintf (stderr, " (rule %d)\n", -*rp - 1);
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}
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fputs ("\n\n", stderr);
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}
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static void
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print_firsts (void)
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{
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fprintf (stderr, "FIRSTS\n");
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for (symbol_number i = ntokens; i < nsyms; ++i)
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{
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fprintf (stderr, " %s firsts\n", symbols[i]->tag);
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bitset_iterator iter;
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symbol_number j;
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BITSET_FOR_EACH (iter, FIRSTS (i), j, 0)
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fprintf (stderr, " %s\n", symbols[j + ntokens]->tag);
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}
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fprintf (stderr, "\n\n");
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}
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static void
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print_fderives (void)
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{
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fprintf (stderr, "FDERIVES\n");
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for (symbol_number i = ntokens; i < nsyms; ++i)
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{
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fprintf (stderr, " %s derives\n", symbols[i]->tag);
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bitset_iterator iter;
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rule_number r;
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BITSET_FOR_EACH (iter, FDERIVES (i), r, 0)
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{
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fprintf (stderr, " %3d ", r);
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rule_rhs_print (&rules[r], stderr);
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fprintf (stderr, "\n");
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}
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}
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fprintf (stderr, "\n\n");
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}
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/*------------------------------------------------------------------.
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| Set FIRSTS to be an NVARS array of NVARS bitsets indicating which |
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| items can represent the beginning of the input corresponding to |
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| which other items. |
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| |
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| For example, if some rule expands symbol 5 into the sequence of |
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| symbols 8 3 20, the symbol 8 can be the beginning of the data for |
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| symbol 5, so the bit [8 - ntokens] in first[5 - ntokens] (= FIRST |
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| (5)) is set. |
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`------------------------------------------------------------------*/
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static void
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set_firsts (void)
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{
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firsts = bitsetv_create (nvars, nvars, BITSET_FIXED);
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for (symbol_number i = ntokens; i < nsyms; ++i)
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for (symbol_number j = 0; derives[i - ntokens][j]; ++j)
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{
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item_number sym = derives[i - ntokens][j]->rhs[0];
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if (ISVAR (sym))
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bitset_set (FIRSTS (i), sym - ntokens);
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}
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if (trace_flag & trace_sets)
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bitsetv_matrix_dump (stderr, "RTC: Firsts Input", firsts);
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bitsetv_reflexive_transitive_closure (firsts);
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if (trace_flag & trace_sets)
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bitsetv_matrix_dump (stderr, "RTC: Firsts Output", firsts);
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if (trace_flag & trace_sets)
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print_firsts ();
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}
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/*-------------------------------------------------------------------.
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| Set FDERIVES to an NVARS by NRULES matrix of bits indicating which |
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| rules can help derive the beginning of the data for each |
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| nonterminal. |
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| |
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| For example, if symbol 5 can be derived as the sequence of symbols |
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| 8 3 20, and one of the rules for deriving symbol 8 is rule 4, then |
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| the [5 - NTOKENS, 4] bit in FDERIVES is set. |
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`-------------------------------------------------------------------*/
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static void
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set_fderives (void)
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{
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fderives = bitsetv_create (nvars, nrules, BITSET_FIXED);
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set_firsts ();
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for (symbol_number i = ntokens; i < nsyms; ++i)
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for (symbol_number j = ntokens; j < nsyms; ++j)
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if (bitset_test (FIRSTS (i), j - ntokens))
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for (rule_number k = 0; derives[j - ntokens][k]; ++k)
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bitset_set (FDERIVES (i), derives[j - ntokens][k]->number);
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if (trace_flag & trace_sets)
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print_fderives ();
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bitsetv_free (firsts);
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}
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void
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closure_new (int n)
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{
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itemset = xnmalloc (n, sizeof *itemset);
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ruleset = bitset_create (nrules, BITSET_FIXED);
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set_fderives ();
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}
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void
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closure (item_number const *core, size_t n)
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{
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if (trace_flag & trace_closure)
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closure_print ("input", core, n);
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bitset_zero (ruleset);
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for (size_t c = 0; c < n; ++c)
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if (ISVAR (ritem[core[c]]))
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bitset_or (ruleset, ruleset, FDERIVES (ritem[core[c]]));
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/* core is sorted on item index in ritem, which is sorted on rule number.
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Compute itemset with the same sort. */
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nitemset = 0;
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size_t c = 0;
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/* A bit index over RULESET. */
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rule_number ruleno;
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bitset_iterator iter;
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BITSET_FOR_EACH (iter, ruleset, ruleno, 0)
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{
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item_number itemno = rules[ruleno].rhs - ritem;
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while (c < n && core[c] < itemno)
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{
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itemset[nitemset] = core[c];
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nitemset++;
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c++;
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}
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itemset[nitemset] = itemno;
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nitemset++;
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};
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while (c < n)
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{
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itemset[nitemset] = core[c];
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nitemset++;
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c++;
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}
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if (trace_flag & trace_closure)
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closure_print ("output", itemset, nitemset);
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}
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void
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closure_free (void)
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{
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free (itemset);
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bitset_free (ruleset);
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bitsetv_free (fderives);
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}
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