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Solver subproject in the Theta model checking framework

There is a newer version: 6.5.2

/*
 *  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.solver.impl;

import static com.google.common.base.Preconditions.checkArgument;

import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import hu.bme.mit.theta.solver.Stack;

public class StackImpl implements Stack {

    public final List items;
    private final List sizes;

    public StackImpl() {
        items = new LinkedList<>();
        sizes = new LinkedList<>();
    }

    @Override
    public void add(final T elem) {
        items.add(elem);
    }

    @Override
    public void add(final Collection elems) {
        items.addAll(elems);
    }

    @Override
    public void push() {
        sizes.add(items.size());
    }

    @Override
    public void pop(final int n) {
        checkArgument(n > 0, "Number of pops must be positive");
        final int depth = sizes.size();
        checkArgument(depth >= n, "Stack not deep enough to pop " + n);

        final int size = sizes.get(depth - n);
        sizes.subList(depth - n, depth).clear();
        items.subList(size, items.size()).clear();
    }

    @Override
    public Collection toCollection() {
        return Collections.unmodifiableCollection(items);
    }

    @Override
    public Iterator iterator() {
        return items.iterator();
    }

    @Override
    public void clear() {
        items.clear();
        sizes.clear();
    }
}