001 /*
002 * Created on Sep 20, 2004
003 *
004 */
005 package aima.logic.fol;
006
007 import java.util.LinkedHashSet;
008 import java.util.Set;
009
010 import aima.logic.fol.kb.data.Chain;
011 import aima.logic.fol.kb.data.Clause;
012 import aima.logic.fol.kb.data.Literal;
013 import aima.logic.fol.parsing.FOLVisitor;
014 import aima.logic.fol.parsing.ast.ConnectedSentence;
015 import aima.logic.fol.parsing.ast.Constant;
016 import aima.logic.fol.parsing.ast.Function;
017 import aima.logic.fol.parsing.ast.NotSentence;
018 import aima.logic.fol.parsing.ast.Predicate;
019 import aima.logic.fol.parsing.ast.QuantifiedSentence;
020 import aima.logic.fol.parsing.ast.Sentence;
021 import aima.logic.fol.parsing.ast.Term;
022 import aima.logic.fol.parsing.ast.TermEquality;
023 import aima.logic.fol.parsing.ast.Variable;
024
025 /**
026 * @author Ravi Mohan
027 * @author Ciaran O'Reilly
028 */
029 public class VariableCollector implements FOLVisitor {
030
031 public VariableCollector() {
032 }
033
034 // Note: The set guarantees the order in which they were
035 // found.
036 public Set<Variable> collectAllVariables(Sentence sentence) {
037 Set<Variable> variables = new LinkedHashSet<Variable>();
038
039 sentence.accept(this, variables);
040
041 return variables;
042 }
043
044 public Set<Variable> collectAllVariables(Term aTerm) {
045 Set<Variable> variables = new LinkedHashSet<Variable>();
046
047 aTerm.accept(this, variables);
048
049 return variables;
050 }
051
052 public Set<Variable> collectAllVariables(Clause aClause) {
053 Set<Variable> variables = new LinkedHashSet<Variable>();
054
055 for (Literal l : aClause.getLiterals()) {
056 l.getAtomicSentence().accept(this, variables);
057 }
058
059 return variables;
060 }
061
062 public Set<Variable> collectAllVariables(Chain aChain) {
063 Set<Variable> variables = new LinkedHashSet<Variable>();
064
065 for (Literal l : aChain.getLiterals()) {
066 l.getAtomicSentence().accept(this, variables);
067 }
068
069 return variables;
070 }
071
072 @SuppressWarnings("unchecked")
073 public Object visitVariable(Variable var, Object arg) {
074 Set<Variable> variables = (Set<Variable>) arg;
075 variables.add(var);
076 return var;
077 }
078
079 @SuppressWarnings("unchecked")
080 public Object visitQuantifiedSentence(QuantifiedSentence sentence,
081 Object arg) {
082 // Ensure I collect quantified variables too
083 Set<Variable> variables = (Set<Variable>) arg;
084 variables.addAll(sentence.getVariables());
085
086 sentence.getQuantified().accept(this, arg);
087
088 return sentence;
089 }
090
091 public Object visitPredicate(Predicate predicate, Object arg) {
092 for (Term t : predicate.getTerms()) {
093 t.accept(this, arg);
094 }
095 return predicate;
096 }
097
098 public Object visitTermEquality(TermEquality equality, Object arg) {
099 equality.getTerm1().accept(this, arg);
100 equality.getTerm2().accept(this, arg);
101 return equality;
102 }
103
104 public Object visitConstant(Constant constant, Object arg) {
105 return constant;
106 }
107
108 public Object visitFunction(Function function, Object arg) {
109 for (Term t : function.getTerms()) {
110 t.accept(this, arg);
111 }
112 return function;
113 }
114
115 public Object visitNotSentence(NotSentence sentence, Object arg) {
116 sentence.getNegated().accept(this, arg);
117 return sentence;
118 }
119
120 public Object visitConnectedSentence(ConnectedSentence sentence, Object arg) {
121 sentence.getFirst().accept(this, arg);
122 sentence.getSecond().accept(this, arg);
123 return sentence;
124 }
125 }