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bdd_to_formula: add CNF variant

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* spot/twa/formula2bdd.hh,
spot/twa/formula2bdd.cc (bdd_to_cnf_formula): New function.
* python/spot/__init__.py: Add a default dictionary for convenience.
* tests/python/bdditer.py: Add test cases.
* NEWS: Mention it.
This commit is contained in:
Alexandre Duret-Lutz 2023-02-23 11:53:07 +01:00
parent 8a5b86521c
commit 66839b1a29
5 changed files with 111 additions and 16 deletions
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32
spot/twa/formula2bdd.cc
View file

@ -1,5 +1,5 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2009-2019 Laboratoire de Recherche et Développement
// Copyright (C) 2009-2019, 2023 Laboratoire de Recherche et Développement
// de l'Epita (LRDE).
// Copyright (C) 2003, 2004 Laboratoire d'Informatique de Paris
// 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
@ -30,11 +30,14 @@ namespace spot
namespace
{
// Convert a BDD which is known to be a conjonction into a formula.
// If dual is true, dualize the result, i.e., negate literals, and
// exchange ∧ and ∨.
template<bool dual>
static formula
conj_to_formula(bdd b, const bdd_dict_ptr d)
{
if (b == bddfalse)
return formula::ff();
return dual ? formula::tt() : formula::ff();
std::vector<formula> v;
while (b != bddtrue)
{
@ -49,11 +52,14 @@ namespace spot
bdd high = bdd_high(b);
if (high == bddfalse)
{
res = formula::Not(res);
if (!dual)
res = formula::Not(res);
b = bdd_low(b);
}
else
{
if (dual)
res = formula::Not(res);
// If bdd_low is not false, then b was not a conjunction.
assert(bdd_low(b) == bddfalse);
b = high;
@ -61,7 +67,7 @@ namespace spot
assert(b != bddfalse);
v.emplace_back(res);
}
return formula::And(v);
return dual ? formula::Or(v) : formula::And(v);
}
} // anonymous
@ -143,7 +149,23 @@ namespace spot
minato_isop isop(f);
bdd cube;
while ((cube = isop.next()) != bddfalse)
v.emplace_back(conj_to_formula(cube, d));
v.emplace_back(conj_to_formula<false>(cube, d));
return formula::Or(std::move(v));
}
formula
bdd_to_cnf_formula(bdd f, const bdd_dict_ptr d)
{
if (f == bddtrue)
return formula::tt();
std::vector<formula> v;
minato_isop isop(!f);
bdd cube;
while ((cube = isop.next()) != bddfalse)
v.emplace_back(conj_to_formula<true>(cube, d));
return formula::And(std::move(v));
}
}

23
spot/twa/formula2bdd.hh
View file

@ -1,5 +1,5 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2012, 2013, 2014, 2015 Laboratoire de Recherche et
// Copyright (C) 2012-2015, 2023 Laboratoire de Recherche et
// Développement de l'Epita (LRDE).
// Copyright (C) 2003 Laboratoire d'Informatique de Paris 6 (LIP6),
// département Systèmes Répartis Coopératifs (SRC), Université Pierre
@ -52,12 +52,21 @@ namespace spot
/// \brief Convert a BDD into a formula.
///
/// Format the BDD as an irredundant sum of product (see the
/// minato_isop class for details) and map the BDD variables back
/// into their atomic propositions. This works only for Boolean
/// formulas, and all the BDD variables used in \a f should have
/// been registered in \a d. Although the result has type
/// formula, it obviously does not use any temporal operator.
/// Format the BDD as a Boolean spot::formula object. This works only
/// for Boolean formulas, and all the BDD variables used in \a f
/// should have been registered in \a d. Although the result has
/// type formula, it obviously does not use any temporal operator.
///
/// The bdd_to_formula() version produces an irredundant sum of
/// product (see the minato_isop class for details) and map the BDD
/// variables back into their atomic propositions.
///
/// The bdd_to_cnf_formula() version produces an irredundant product of
/// sum, using the dual construction.
/// @{
SPOT_API
formula bdd_to_formula(bdd f, const bdd_dict_ptr d);
SPOT_API
formula bdd_to_cnf_formula(bdd f, const bdd_dict_ptr d);
/// @}
}