// checks that the atom has the form f(x) = t[x],
// where f is a function symbol and t[x] is a term of x not containing f
// 09/05/2002, Manchester
bool Atom::isDefinition (Term& lhs, Term& rhs) const
{
TRACER ( "Atom::isDefinition" );
if ( ! isEquality() ) {
return false;
}
// the atom is an equality
Term l (args().head());
Term r (args().second());
if ( l.isvar() || r.isvar() ) {
return false;
}
// l=r, both l and r are non-variables
if ( r.defines(l) ) {
lhs = l;
rhs = r;
return true;
}
if ( l.defines(r) ) {
rhs = l;
lhs = r;
return true;
}
return false;
} // Term* Atom::isDefinition
// comparison of two atoms, needed to normalize
// 28/08/2002 Torrevieja
Compare Atom::compare ( Atom a ) const
{
// equality is less than nonequality
if ( isEquality() ) {
if ( ! a.isEquality() )
return LESS;
}
else if ( a.isEquality() ) {
return GREATER;
}
// now either both are equality or both are not equality
switch ( functor()->compare(a.functor()) ) {
case LESS:
return LESS;
case EQUAL:
return args().compare(a.args());
case GREATER:
return GREATER;
#if DEBUG_PREPRO
default:
ASS(false);
#endif
}
} // Atom::compare
// return true if the atom is t = t
// 29/04/2002 Manchester
bool Atom::isTautology () const
{
TRACER("Atom::isTautology");
if ( ! isEquality() )
return false;
return args().head().equal(args().second());
} // Atom::isTautology
bool Logic::isAtom(PTRef r) const {
Pterm& t = term_store[r];
if (sym_store[t.symb()].rsort() == getSort_bool()) {
if (t.size() == 0) return true;
if (t.symb() == getSym_not() ) return false;
// At this point all arguments of equivalence have the same sort. Check only the first
if (isEquality(t.symb()) && (sym_store[term_store[t[0]].symb()].rsort() != getSort_bool())) return true;
if (isUP(r)) return true;
}
return false;
}
// true if this is t1 = t2 and a is t2 = t1
// 29/04/2002, Manchester
// 28/08/2002 Torrevieja changed
bool Atom::swap (Atom a) const
{
TRACER("Atom::swap");
if ( ! isEquality() )
return false;
if ( ! a.isEquality() )
return false;
return args().head().equal (a.args().second()) &&
a.args().head().equal(args().second());
} // Atom::swap
// A term is literal if its sort is Bool and
// (i) number of arguments is 0
// (ii) its symbol is sym_NOT and argument is a literal (nested nots
// create literals?)
// (iii) it is an atom stating an equivalence of non-boolean terms (terms must be purified at this point)
bool Logic::isLit(PTRef tr) const
{
Pterm& t = getPterm(tr);
if (sym_store[t.symb()].rsort() == getSort_bool()) {
if (t.size() == 0) return true;
if (t.symb() == getSym_not() ) return isLit(t[0]);
// At this point all arguments of equivalence have the same sort. Check only the first
if (isEquality(tr) && (sym_store[getPterm(t[0]).symb()].rsort() != getSort_bool())) return true;
if (isUP(tr)) return true;
}
return false;
}
// Uninterpreted predicate p : U U* -> Bool
bool Logic::isUP(PTRef ptr) const {
Pterm& t = term_store[ptr];
SymRef sr = t.symb();
// Should this really be an uninterpreted predicate?
// At least it falsely identifies (= true false) as an uninterpreted
// predicate without the extra condition
if (isEquality(sr) || isDisequality(sr)) {
if (isBooleanOperator(sr)) return false;
else return true;
}
Symbol& sym = sym_store[sr];
if (sym.nargs() == 0) return false;
if (sym.rsort() != getSort_bool()) return false;
if (isBooleanOperator(sr)) return false;
return true;
}
// normalize the atom
// 29/08/2002 Torrevieja, changed
void Atom::normalize ()
{
if ( ! isEquality() ) {
return;
}
// equality
TermList as (args());
Term l (as.head());
Term r (as.second());
if (l.compare(r) == LESS) {
TermList newAs (r, TermList (l));
Atom newAtom (functor(), newAs);
*this = newAtom;
}
} // Atom::normalize
// Adds the uninterpreted predicate if ptr is an uninterpreted predicate.
// Returns reference to corresponding equality term or PTRef_Undef. Creates
// the eq term if it does not exist.
// If the term is an equality (disequality), it must be an equality
// (disequality) over terms with non-boolean return type. Those must be then
// returned as is.
PTRef Logic::lookupUPEq(PTRef ptr) {
assert(isUP(ptr));
// already seen
if (UP_map.contains(ptr)) return UP_map[ptr];
// already an equality
Pterm& t = term_store[ptr];
if (isEquality(t.symb()) | isDisequality(t.symb()))
return ptr;
// Create a new equality
// Symbol& sym = sym_store[t.symb()];
vec<PTRef> args;
args.push(ptr);
args.push(getTerm_true());
return mkEq(args);
// return resolveTerm(tk_equals, args);
}
//
// Sort a term if it commutes.
// The following simplifications implemented
// (should be refactored to separate methods?):
// - `and':
// - drop constant true terms
// - convert an empty `and' to the constant term `true'
// - convert an `and' containing `false' to a replicate `false'
// - `or':
// - drop constant false terms
// - convert an empty `or' to a replicate `false' term
// - convert an `or' containing `true' to a replicate `true'
//
//
void Logic::simplify(SymRef& s, vec<PTRef>& args) {
// First sort it
#ifdef SORT_BOOLEANS
if (sym_store[s].commutes())
#else
if (sym_store[s].commutes() && !isAnd(s) && !isOr(s))
#endif
sort(args, LessThan_PTRef());
if (!isBooleanOperator(s) && !isEquality(s)) return;
int dropped_args = 0;
bool replace = false;
if (s == getSym_and()) {
int i, j;
PTRef p = PTRef_Undef;
for (i = j = 0; i < args.size(); i++) {
if (args[i] == getTerm_false()) {
args.clear();
s = getSym_false();
#ifdef SIMPLIFY_DEBUG
cerr << "and -> false" << endl;
#endif
return;
} else if (args[i] != getTerm_true() && args[i] != p) {
args[j++] = p = args[i];
} else {
#ifdef SIMPLIFY_DEBUG
cerr << "and -> drop" << endl;
#endif
}
}
dropped_args = i-j;
if (dropped_args == args.size()) {
s = getSym_true();
args.clear();
#ifdef SIMPLIFY_DEBUG
cerr << "and -> true" << endl;
#endif
return;
} else if (dropped_args == args.size() - 1)
replace = true;
else if (dropped_args > 0)
args.shrink(dropped_args);
}
if (s == getSym_or()) {
int i, j;
PTRef p = PTRef_Undef;
for (i = j = 0; i < args.size(); i++) {
if (args[i] == getTerm_true()) {
args.clear();
s = getSym_true();
#ifdef SIMPLIFY_DEBUG
cerr << "or -> true" << endl;
#endif
return;
} else if (args[i] != getTerm_false() && args[i] != p) {
args[j++] = p = args[i];
} else {
#ifdef SIMPLIFY_DEBUG
cerr << "or -> drop" << endl;
#endif
}
}
dropped_args = i-j;
if (dropped_args == args.size()) {
s = getSym_false();
args.clear();
#ifdef SIMPLIFY_DEBUG
cerr << "or -> false" << endl;
#endif
return;
}
else if (dropped_args == args.size() - 1)
replace = true;
else if (dropped_args > 0)
args.shrink(dropped_args);
}
if (isEquality(s)) {
assert(args.size() == 2);
if (isBooleanOperator(s) && (args[0] == getTerm_true())) {
Pterm& t = getPterm(args[1]);
s = t.symb();
args.clear();
for (int i = 0; i < t.size(); i++)
args.push(t[i]);
#ifdef SIMPLIFY_DEBUG
cerr << "eq -> second" << endl;
#endif
return;
} else if (isBooleanOperator(s) && (args[0] == getTerm_false())) {
PTRef old = args[1];
PTRef tr = mkNot(args[1]);
Pterm& t = getPterm(tr);
s = t.symb();
args.clear();
args.push(old);
#ifdef SIMPLIFY_DEBUG
cerr << "eq -> not second" << endl;
#endif
return;
} else if (isBooleanOperator(s) && (args[1] == getTerm_true())) {
args.clear();
Pterm& t = getPterm(args[0]);
s = t.symb();
args.clear();
for (int i = 0; i < t.size(); i++)
args.push(t[i]);
#ifdef SIMPLIFY_DEBUG
cerr << "eq -> first" << endl;
#endif
return;
} else if (isBooleanOperator(s) && (args[1] == getTerm_false())) {
PTRef old = args[0];
PTRef tr = mkNot(args[0]);
Pterm& t = getPterm(tr);
s = t.symb();
args.clear();
args.push(old);
#ifdef SIMPLIFY_DEBUG
cerr << "eq -> not first"<< endl;
#endif
return;
} else if (args[0] == args[1]) {
args.clear();
s = getSym_true();
#ifdef SIMPLIFY_DEBUG
cerr << "eq -> true" << endl;
#endif
return;
} else if (isBooleanOperator(s) && (args[0] == mkNot(args[1]))) {
args.clear();
s = getSym_false();
#ifdef SIMPLIFY_DEBUG
cerr << "eq -> false" << endl;
#endif
return;
}
}
if (isNot(s)) {
if (isTrue(args[0])) {
args.clear();
s = getSym_false();
#ifdef SIMPLIFY_DEBUG
cerr << "not -> false" << endl;
#endif
return;
}
if (isFalse(args[0])) {
args.clear();
s = getSym_true();
#ifdef SIMPLIFY_DEBUG
cerr << "not -> true" << endl;
#endif
return;
}
}
// Others, to be implemented:
// - distinct
// - implies
// - xor
// - ite
if (replace) {
// Return whatever is the sole argument
Pterm& t = getPterm(args[0]);
s = t.symb();
args.clear();
for (int i = 0; i < t.size(); i++)
args.push(t[i]);
#ifdef SIMPLIFY_DEBUG
cerr << " replace" << endl;
#endif
}
}