gov.nasa.jpf.constraints.util.ExpressionRestrictionVisitor.java Source code

Introduction

Here is the source code for gov.nasa.jpf.constraints.util.ExpressionRestrictionVisitor.java

Source

/*
 * Copyright (C) 2015, United States Government, as represented by the 
 * Administrator of the National Aeronautics and Space Administration.
 * All rights reserved.
 *
 * The PSYCO: A Predicate-based Symbolic Compositional Reasoning environment 
 * platform is licensed under the Apache License, Version 2.0 (the "License"); you 
 * may not use this file except in compliance with the License. You may obtain a 
 * copy of the License at http://www.apache.org/licenses/LICENSE-2.0. 
 *
 * Unless required by applicable law or agreed to in writing, software distributed 
 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR 
 * CONDITIONS OF ANY KIND, either express or implied. See the License for the 
 * specific language governing permissions and limitations under the License.
 */

package gov.nasa.jpf.constraints.util;

import gov.nasa.jpf.constraints.api.Expression;
import gov.nasa.jpf.constraints.api.Variable;
import gov.nasa.jpf.constraints.expressions.AbstractExpressionVisitor;
import gov.nasa.jpf.constraints.expressions.PropositionalCompound;
import gov.nasa.jpf.constraints.expressions.QuantifierExpression;

import com.google.common.base.Predicate;
import com.google.common.base.Predicates;

class ExpressionRestrictionVisitor
        extends AbstractExpressionVisitor<Expression<?>, Predicate<? super Variable<?>>> {

    private static final ExpressionRestrictionVisitor INSTANCE = new ExpressionRestrictionVisitor();

    public static ExpressionRestrictionVisitor getInstance() {
        return INSTANCE;
    }

    //private boolean mixedParams = false;

    /* (non-Javadoc)
     * @see gov.nasa.jpf.constraints.expressions.AbstractExpressionVisitor#visit(gov.nasa.jpf.constraints.api.Variable, java.lang.Object)
     */
    @Override
    public <E> Expression<?> visit(Variable<E> v, Predicate<? super Variable<?>> data) {
        return (data.apply(v)) ? v : null;
    }

    /* (non-Javadoc)
     * @see gov.nasa.jpf.constraints.expressions.AbstractExpressionVisitor#visit(gov.nasa.jpf.constraints.expressions.QuantifierExpression, java.lang.Object)
     */
    @Override
    public Expression<?> visit(QuantifierExpression q, Predicate<? super Variable<?>> data) {
        Predicate<Variable<?>> newPred = Predicates.or(Predicates.in(q.getBoundVariables()), data);
        Expression<?> exp = visit(q.getBody(), newPred);
        return (exp != null) ? q.duplicate(new Expression[] { exp }) : null;
    }

    /* (non-Javadoc)
     * @see gov.nasa.jpf.constraints.expressions.AbstractExpressionVisitor#defaultVisit(gov.nasa.jpf.constraints.api.Expression, java.lang.Object)
     */
    @Override
    protected <E> Expression<?> defaultVisit(Expression<E> expression, Predicate<? super Variable<?>> data) {
        Expression<?>[] children = expression.getChildren();
        if (children.length == 0)
            return expression;

        Expression<?> c1 = children[0];
        Expression<?> v1 = visit(c1, data);

        if (children.length == 1)
            return (v1 != null) ? expression.duplicate(new Expression[] { v1 }) : null;

        Expression<?> c2 = children[1];
        Expression<?> v2 = visit(c2, data);
        if (v1 == c1 && v2 == c2)
            return expression;

        if (v1 == null) {
            if (v2 != null && ExpressionUtil.containsVars(v2))
                throw new MixedParamsException();
            return null;
        }
        if (v2 == null) {
            if (ExpressionUtil.containsVars(v1))
                throw new MixedParamsException();
            return null;
        }

        return expression.duplicate(new Expression[] { v1, v2 });
    }

    /* (non-Javadoc)
     * @see gov.nasa.jpf.constraints.expressions.AbstractExpressionVisitor#visit(gov.nasa.jpf.constraints.expressions.PropositionalCompound, java.lang.Object)
     */
    @Override
    @SuppressWarnings("unchecked")
    public Expression<?> visit(PropositionalCompound n, Predicate<? super Variable<?>> data) {
        Expression<Boolean> c1 = n.getLeft();
        Expression<Boolean> v1 = (Expression<Boolean>) visit(c1, data);

        Expression<Boolean> c2 = n.getRight();
        Expression<Boolean> v2 = (Expression<Boolean>) visit(c2, data);
        if (v1 == c1 && v2 == c2)
            return n;

        if (v1 == null)
            return v2;
        if (v2 == null)
            return v1;

        return new PropositionalCompound(v1, n.getOperator(), v2);
    }

    //  public boolean hasMixedParams() {
    //    return mixedParams;
    //  }

    @SuppressWarnings("unchecked")
    public <T> Expression<T> apply(Expression<T> expr, Predicate<? super Variable<?>> pred) {
        return (Expression<T>) visit(expr, pred);
    }

}