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/*
 * Copyright (c) 2002 - 2006 IBM Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 */
package com.ibm.wala.fixpoint;

import com.ibm.wala.util.debug.Assertions;
import com.ibm.wala.util.debug.UnimplementedError;
import org.jspecify.annotations.Nullable;

/** An operator of the form lhs = op (rhs) */
public abstract class UnaryOperator> extends AbstractOperator {

  /**
   * Evaluate this equation, setting a new value for the left-hand side.
   *
   * @return a constant defined by {@link FixedPointConstants} that reflects whether the lhs value
   *     changed
   */
  public abstract byte evaluate(@Nullable T lhs, T rhs);

  /** Create an equation which uses this operator Override in subclasses for efficiency. */
  public UnaryStatement makeEquation(T lhs, T rhs) {
    return new BasicUnaryStatement<>(lhs, this, rhs);
  }

  public boolean isIdentity() {
    return false;
  }

  @Override
  public byte evaluate(T lhs, T[] rhs) throws UnimplementedError {
    // this should never be called. Use the other, more efficient form.
    Assertions.UNREACHABLE();
    return 0;
  }
}