public Operation exec(Prolog engine) {
engine.requireFeature(Prolog.Feature.JAVA_REFLECTION, this, arg1);
engine.setB0();
Term a1, a2, a3;
a1 = arg1;
a2 = arg2;
a3 = arg3;
Class clazz = null;
Object instance = null;
Field field = null;
Object value = null;
try {
// 1st. argument (atom or java term)
a1 = a1.dereference();
if (a1.isVariable()) {
throw new PInstantiationException(this, 1);
} else if (a1.isSymbol()) { // class
clazz = Class.forName(((SymbolTerm) a1).name());
} else if (a1.isJavaObject()) { // instance
instance = ((JavaObjectTerm) a1).object();
clazz = ((JavaObjectTerm) a1).getClazz();
} else {
throw new IllegalTypeException(this, 1, "atom_or_java", a1);
}
// 2nd. argument (atom)
a2 = a2.dereference();
if (a2.isVariable()) {
throw new PInstantiationException(this, 2);
} else if (!a2.isSymbol()) {
throw new IllegalTypeException(this, 2, "atom", a2);
}
field = clazz.getDeclaredField(((SymbolTerm) a2).name());
// 3rd. argument (term)
a3 = a3.dereference();
if (a3.isJavaObject()) value = a3.toJava();
else value = a3;
field.setAccessible(true);
field.set(instance, value);
return cont;
} catch (ClassNotFoundException e) { // Class.forName
throw new JavaException(this, 1, e);
} catch (NoSuchFieldException e) { // Class.getField(..)
throw new JavaException(this, 2, e);
} catch (SecurityException e) { // Class.getField(..)
throw new JavaException(this, 2, e);
} catch (NullPointerException e) { // Class.getField(..)
throw new JavaException(this, 2, e);
} catch (IllegalAccessException e) { // Field.get(..)
throw new JavaException(this, 2, e);
} catch (IllegalArgumentException e) { // Field.get(..)
throw new JavaException(this, 2, e);
}
}
// TODO: update it for rules with non-DL prediciates in the body
public Set<Variable> getNonDistinguishedVars() {
Set<Variable> nonDistinguishedVars = new HashSet<Variable>();
Set<Term> distinguishedVars = this.getDistinguishedVariables();
for (Atom atom : body) {
for (Term term : atom.getTerms())
if (distinguishedVars == null) { // Xiao: can not happen!
if (term.isVariable()) nonDistinguishedVars.add((Variable) term);
} else if ((term.isVariable()) && !distinguishedVars.contains(term))
nonDistinguishedVars.add((Variable) term);
}
return nonDistinguishedVars;
}
public Set<Term> getDistinguishedVariables() {
Set<Term> vars = new HashSet<Term>();
for (Term term : this.head.getTerms()) {
if (term.isVariable()) vars.add(term);
}
return vars;
}
/* Term */
public boolean unify(Term t, Trail trail) {
t = t.dereference();
if (t.isVariable()) {
((VariableTerm) t).bind(this, trail);
return true;
}
return eq(this, t);
}
/**
* Compares two terms in <em>Prolog standard order of terms</em>.<br>
* It is noted that <code>t1.compareTo(t2) == 0</code> has the same <code>boolean</code> value as
* <code>t1.equals(t2)</code>.
*
* @param anotherTerm the term to compared with. It must be dereferenced.
* @return the value <code>0</code> if two terms are identical; a value less than <code>0</code>
* if this term is <em>before</em> the <code>anotherTerm</code>; and a value greater than
* <code>0</code> if this term is <em>after</em> the <code>anotherTerm</code>.
*/
public int compareTo(Term anotherTerm) { // anotherTerm must be dereferenced.
if (anotherTerm.isVariable() || anotherTerm.isNumber()) return AFTER;
if (!anotherTerm.isSymbol()) return BEFORE;
if (this == anotherTerm) return EQUAL;
int x = name.compareTo(((SymbolTerm) anotherTerm).name());
if (x != 0) return x;
int y = this.arity - ((SymbolTerm) anotherTerm).arity();
if (y != 0) return y;
throw new InternalException("SymbolTerm is not unique");
}
public CQ computeQprime(TIntHashSet type, Variable x) {
CQ qPrime = new CQ();
qPrime.setHead(head);
int numberOfIndividual = 0;
Constant individual = new Constant();
for (Term term : this.computeRenamingVars(x)) {
if (!term.isVariable()) {
numberOfIndividual++;
individual = (Constant) term;
}
}
if (numberOfIndividual > 1) // cannot merge two individuals
return null;
// if there is no individual in the variables which should be renamed
if (numberOfIndividual == 0) {
for (Atom atom : body) { // compute body
if (!(atom.getTerms().contains(x))) {
// atom that contains x will disappear in the rewrite query
List<Term> newTerms = new ArrayList<Term>();
for (Term term : atom.getTerms()) {
if (this.computeRenamingVars(x).contains(term)) newTerms.add(x);
else newTerms.add(term);
}
Atom renamedVarAtom = new Atom(atom.getPredicate(), newTerms);
if (!qPrime.body.contains(renamedVarAtom)) {
qPrime.body.add(renamedVarAtom);
}
}
}
// add type(x) to the body
Set<Atom> currentBody = qPrime.getBody();
qPrime.body.addAll(addTypeOfXToBody(x, type, currentBody));
// compute head
Atom newHead = computeNewHead(x, this.head);
qPrime.setHead(newHead);
}
// if there is an individual in the variables which should be renamed
// then all these variables should be renamed as the individual
if (numberOfIndividual == 1) {
// compute body
for (Atom atom : body) {
if (!(atom.getTerms().contains(x))) {
// atom that contains x will disappear in the rewrite query
List<Term> newTerms = new ArrayList<Term>();
for (Term term : atom.getTerms()) {
if (this.computeRenamingVars(x).contains(term))
// this term should be renamed
newTerms.add(individual);
else newTerms.add(term);
}
Atom renamedVarAtom = new Atom(atom.getPredicate(), newTerms);
if (!qPrime.body.contains(renamedVarAtom)) {
qPrime.body.add(renamedVarAtom);
}
}
}
// at type(x) to the body
Set<Atom> currentBody = qPrime.getBody();
qPrime.body.addAll(addTypeOfXToBody(individual, type, currentBody));
// compute head
Atom newHead = computeNewHead(x, individual, this.head);
qPrime.setHead(newHead);
}
return qPrime;
}