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Add a new library to generate formulas and automata.

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This library, called libspotgen, gathers functions to generate classes
of automata found in the literature.
Related to #254.

* NEWS, README: Mention the modification.
* Makefile.am, debian/control, debian/libspotgen0.install: Build the new
  library in a separate package.
* spot/gen/automata.hh, spot/gen/automata.cc: Add a family of co-Büchi
  automata.
* configure.ac, spot/Makefile.am, spot/gen/Makefile.am: Build the new
  library.
This commit is contained in:
Maximilien Colange 2017-04-21 17:11:21 +02:00
parent b428ed31ec
commit d90e38eb2a
10 changed files with 188 additions and 5 deletions
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// -*- coding: utf-8 -*-
// Copyright (C) 2017 Laboratoire de Recherche et Developpement de
// l'EPITA (LRDE).
//
// This file is part of Spot, a model checking library.
//
// Spot 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.
//
// Spot 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 <spot/gen/automata.hh>
#include <spot/twa/formula2bdd.hh>
#include <spot/tl/parse.hh>
namespace spot
{
namespace gen
{
twa_graph_ptr
ks_cobuchi(unsigned n)
{
// the alphabet has four letters:
// i, s (for sigma), p (for pi), h (for hash)
// we encode this four letters alphabet thanks to two AP a and b
// the exact encoding is not important
// each letter is a permutation of the set {1..2n}
// s = (1 2 .. 2n) the rotation
// p = (1 2) the swap of the first two elements
// i is the identity
// d is the identity on {2..2n} but is undefined on 1
// the automaton has 2n+1 states, numbered from 0 to 2n
// 0 is the initial state and the only non-deterministic state
auto dict = make_bdd_dict();
auto aut = make_twa_graph(dict);
// register aps
aut->register_ap("a");
aut->register_ap("b");
// retrieve the four letters, and name them
bdd i = formula_to_bdd(parse_formula("a&&b"), dict, aut);
bdd s = formula_to_bdd(parse_formula("a&&!b"), dict, aut);
bdd p = formula_to_bdd(parse_formula("!a&&b"), dict, aut);
bdd h = formula_to_bdd(parse_formula("!a&&!b"), dict, aut);
// actually build the automaton
aut->new_states(2*n+1);
aut->set_init_state(0);
aut->set_acceptance(1, acc_cond::acc_code::cobuchi());
// from 0, we can non-deterministically jump to any state (except 0) with
// any letter.
for (unsigned q = 1; q <= 2*n; ++q)
aut->new_edge(0, q, bddtrue, {0});
// i is the identity
for (unsigned q = 1; q <= 2*n; ++q)
aut->new_edge(q, q, i);
// p swaps 1 and 2, and leaves all other states invariant
aut->new_edge(1, 2, p);
aut->new_edge(2, 1, p);
for (unsigned q = 3; q <= 2*n; ++q)
aut->new_edge(q, q, p);
// s does to next state (mod 2*n, 0 excluded)
aut->new_edge(2*n, 1, s);
for (unsigned q = 1; q < 2*n; ++q)
aut->new_edge(q, q+1, s);
// h is the same as i, except on 1 where it goes back to the initial state
aut->new_edge(1, 0, h);
for (unsigned q = 2; q <= 2*n; ++q)
aut->new_edge(q, q, h);
aut->merge_edges();
return aut;
}
}
}