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 * All rights reserved.
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 * modification, are permitted provided that the following conditions
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 *
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 *   notice, this list of conditions and the following disclaimer.
 *
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 *   notice, this list of conditions and the following disclaimer in
 *   the documentation and/or other materials provided with the
 *   distribution.  
 *
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 *   the names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior 
 *   written permission.
 *
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package blog;

import java.util.*;
import common.HashMapDiff;

public class ExistentialFormula extends Formula{

    

    public ExistentialFormula( String varName, Type varType, Formula cond ){
	var = new LogicalVar(varName, varType);
	this.cond = cond;
    }

    public ExistentialFormula(LogicalVar var, Formula cond) {
	this.var = var;
	this.cond = cond;
    }

    

    public LogicalVar getLogicalVariable() {
	return var;
    }

    

    public Type getType() {
	return var.getType();
    }

    

    public Formula getCond() {
	return cond;
    }

    public Object evaluate(EvalContext context) {
	context.pushEvaluee(this);

	ObjectSet witnesses = getWitnessSpec().elementSet(context);
	Boolean result = null;
	if (witnesses.canDetermineIsEmpty()) {
	    result = Boolean.valueOf(!witnesses.isEmpty());
	    if (witnessSpec.dependsOnIdOrder(context)) {
		System.out.println
		    ("Warning: Short-circuiting an iteration that depends on "
		     + "order of object identifiers, while evaluating " 
		     + this + ".  MCMC states may define overlapping events.");
	    }
	}

	context.popEvaluee();
	return result;
    }

    public boolean containsRandomSymbol() {
	return true; // the type symbol
    }

    public boolean checkTypesAndScope(Model model, Map scope) {
	Map extendedScope = new HashMapDiff(scope);
	extendedScope.put(var.getName(), var);
	return cond.checkTypesAndScope(model, extendedScope);
    }

    

    public int compile(LinkedHashSet callStack) {
	callStack.add(this);
	int errors = cond.compile(callStack);
	if (errors > 0) {
	    return errors;
	}

	witnessSpec = new CompiledSetSpec(var, cond);
	callStack.remove(this);
	return 0;
    }

    

    public Formula getStandardForm() {
	return new ExistentialFormula(var, cond.getStandardForm());
    }

    

    protected Formula getEquivToNegationInternal() {
	return new UniversalFormula(var, new NegFormula(cond));
    }

    public List getSubformulas() {
	return Collections.singletonList(cond);
    }

    public Set getFreeVars() {
	Set freeVars = new HashSet(cond.getFreeVars());
	freeVars.remove(var);
	return Collections.unmodifiableSet(freeVars);
    }

    public boolean isQuantified() {
	return true;
    }

    public Set getSatisfiersIfExplicit(EvalContext context, 
				       LogicalVar subject,
				       GenericObject genericObj) {
	Set satisfiers = null;
	boolean createdNewSet = false;

	// We use an unfiltered iterator over possible values of the 
	// quantified variable because the set of quantified-variable 
	// values that satisfy cond often depends on the value of subject.  
	// We hope the ObjGenGraphs used for the unfiltered iterator don't 
	// use subject (if they do, canDetermineNext will return false).  
	ObjectIterator iter = getWitnessSpec().unfilteredIterator(context);
	while (iter.hasNext()) {
	    Object varValue = iter.next();
	    context.assign(var, varValue);
	    Set condSat = cond.getSatisfiersIfExplicit
		(context, subject, genericObj);
	    if (condSat == Formula.ALL_OBJECTS) {
		// Short-circuit: all objects make cond true with this 
		// value of the quantified variable, so no point in looking 
		// at other values.  
		return Formula.ALL_OBJECTS;
	    }
	    if (condSat != null) {
		// Subject values that make cond true with this value of 
		// the quantified variable thereby make the whole 
		// existential formula true.  
		if (satisfiers == null) {
		    satisfiers = condSat;
		} else {
		    if (!createdNewSet) {
		        // in case satisfiers was unmodifiable...
			satisfiers = new LinkedHashSet(satisfiers);
			createdNewSet = true;
		    }
		    satisfiers.addAll(condSat);
		} 
	    }
	}
	context.unassign(var);
	if (!iter.canDetermineNext()) {
	    return null;
	}
		
	return satisfiers;
    }

    public ArgSpec getSubstResult(Substitution subst, 
				  Set<LogicalVar> boundVars) {
	boundVars = new HashSet<LogicalVar>(boundVars);
	boundVars.add(var);
	return new ExistentialFormula
	    (var, (Formula) cond.getSubstResult(subst, boundVars));
    }

    public String toString() {
	return ("exists " + var.getType() + " " + var.getName() 
		+ " (" + cond + ")");
    }

    public boolean equals(Object o) {
	if (o instanceof ExistentialFormula) {
	    ExistentialFormula other = (ExistentialFormula) o;
	    return (var.equals(other.getLogicalVariable())
		    && cond.equals(other.getCond()));
	}
	return false;
    }

    public int hashCode() {
	return (getClass().hashCode() ^ var.hashCode() ^ cond.hashCode());
    }

    

    protected CompiledSetSpec getWitnessSpec() {
	if (witnessSpec == null) {
	    compile(new LinkedHashSet());
	}
	return witnessSpec;
    }

    private LogicalVar var;
    private Formula cond;

    private CompiledSetSpec witnessSpec;
} 

This file was generated on Tue Jun 08 17:53:36 PDT 2010 from file ExistentialFormula.java
by the ilog.language.tools.Hilite Java tool written by Hassan Aït-Kaci