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Sts subproject in the Theta model checking framework

There is a newer version: 6.8.5

/*
 *  Copyright 2024 Budapest University of Technology and Economics
 *
 *  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 hu.bme.mit.theta.sts;

import hu.bme.mit.theta.core.type.Expr;
import hu.bme.mit.theta.core.type.booltype.BoolType;
import hu.bme.mit.theta.core.utils.ExprUtils;

/**
 * Utilities related to the STS formalism.
 */
public final class StsUtils {

    private StsUtils() {
    }

    /**
     * Transform STS into an equivalent new STS, without if-then-else constructs.
     *
     * @param sts Original STS
     * @return Transformed STS
     */
    public static STS eliminateIte(final STS sts) {
        final STS.Builder builder = STS.builder();
        builder.addInit(ExprUtils.eliminateIte(sts.getInit()));
        builder.addTrans(ExprUtils.eliminateIte(sts.getTrans()));
        builder.setProp(ExprUtils.eliminateIte(sts.getProp()));
        return builder.build();
    }

    /**
     * Transform STS into a new STS, where the initial and transition formula is in an
     * equisatisfiable CNF form. The property is not transformed (as it may be negated).
     *
     * @param sts Original STS
     * @return Transformed STS
     */
    public static STS transformToCnf(final STS sts) {
        final STS.Builder builder = STS.builder();
        builder.addInit(transformIfNonCNF(sts.getInit()));
        builder.addTrans(transformIfNonCNF(sts.getTrans()));
        builder.setProp(sts.getProp());
        return builder.build();
    }

    private static Expr transformIfNonCNF(final Expr expr) {
        if (ExprUtils.isExprCnf(expr)) {
            return expr;
        } else {
            return ExprUtils.transformEquiSatCnf(expr);
        }
    }
}