AbstractExpression.java

/*
 * Portions of this software was developed by employees of the National Institute
 * of Standards and Technology (NIST), an agency of the Federal Government and is
 * being made available as a public service. Pursuant to title 17 United States
 * Code Section 105, works of NIST employees are not subject to copyright
 * protection in the United States. This software may be subject to foreign
 * copyright. Permission in the United States and in foreign countries, to the
 * extent that NIST may hold copyright, to use, copy, modify, create derivative
 * works, and distribute this software and its documentation without fee is hereby
 * granted on a non-exclusive basis, provided that this notice and disclaimer
 * of warranty appears in all copies.
 *
 * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
 * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
 * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
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 * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
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 * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
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package gov.nist.secauto.metaschema.core.metapath;

import gov.nist.secauto.metaschema.core.metapath.function.FunctionUtils;
import gov.nist.secauto.metaschema.core.metapath.function.library.FnData;
import gov.nist.secauto.metaschema.core.metapath.item.IItem;
import gov.nist.secauto.metaschema.core.metapath.item.atomic.IAnyAtomicItem;

import edu.umd.cs.findbugs.annotations.NonNull;
import edu.umd.cs.findbugs.annotations.Nullable;

abstract class AbstractExpression implements IExpression {
  /**
   * Get the first data item of the provided {@code sequence} cast to an
   * {@link IAnyAtomicItem}.
   *
   * @param sequence
   *          the sequence to get the data item from
   * @param requireSingleton
   *          if {@code true} then a {@link TypeMetapathException} is thrown if
   *          the sequence contains more than one item
   * @return {@code null} if the sequence is empty, or the item otherwise
   * @throws TypeMetapathException
   *           if the sequence contains more than one item and requireSingleton is
   *           {@code true}, or if the data item cannot be cast
   */
  @Nullable
  public static IAnyAtomicItem getFirstDataItem(@NonNull ISequence<?> sequence,
      boolean requireSingleton) {
    IItem item = FunctionUtils.getFirstItem(sequence, requireSingleton);

    return item == null ? null : FnData.fnDataItem(item);
  }

  @Override
  public String toString() {
    return ASTPrinter.instance().visit(this);
  }
}