Package org.exist.xquery.functions.fn

Source Code of org.exist.xquery.functions.fn.FunHeadTail

package org.exist.xquery.functions.fn;

import org.exist.dom.ExtArrayNodeSet;
import org.exist.dom.NodeSet;
import org.exist.dom.QName;
import org.exist.xquery.AnalyzeContextInfo;
import org.exist.xquery.BasicFunction;
import org.exist.xquery.Cardinality;
import org.exist.xquery.ErrorCodes;
import org.exist.xquery.Function;
import org.exist.xquery.FunctionSignature;
import org.exist.xquery.XPathException;
import org.exist.xquery.XQueryContext;
import org.exist.xquery.value.FunctionParameterSequenceType;
import org.exist.xquery.value.FunctionReturnSequenceType;
import org.exist.xquery.value.Sequence;
import org.exist.xquery.value.SequenceType;
import org.exist.xquery.value.Type;
import org.exist.xquery.value.ValueSequence;

public class FunHeadTail extends BasicFunction {

  public final static FunctionSignature signatures[] = {
        new FunctionSignature(
            new QName("head", Function.BUILTIN_FUNCTION_NS),
            "The function returns the value of the expression $arg[1], i.e. the first item in the " +
            "passed in sequence.",
            new SequenceType[] {
                new FunctionParameterSequenceType("arg", Type.ITEM, Cardinality.ZERO_OR_MORE, "")
            },
            new FunctionReturnSequenceType(Type.ITEM, Cardinality.ZERO_OR_ONE, "the first item or the empty sequence")),
        new FunctionSignature(
                new QName("tail", Function.BUILTIN_FUNCTION_NS),
                "The function returns the value of the expression subsequence($sequence, 2), i.e. a new sequence containing " +
                "all items of the input sequence except the first.",
                new SequenceType[] {
                    new FunctionParameterSequenceType("sequence", Type.ITEM, Cardinality.ZERO_OR_MORE, "The source sequence")
                    },
                new FunctionReturnSequenceType(Type.ITEM, Cardinality.ZERO_OR_MORE, "the resulting sequence")) };
 
  public FunHeadTail(XQueryContext context, FunctionSignature signature) {
    super(context, signature);
  }

  @Override
  public void analyze(AnalyzeContextInfo contextInfo) throws XPathException {
    super.analyze(contextInfo);
    if (getContext().getXQueryVersion()<30) {
      throw new XPathException(this, ErrorCodes.EXXQDY0003, "Function " +
          getSignature().getName() + " is only supported for xquery version \"3.0\" and later.");
    }
  }
 
  @Override
  public Sequence eval(Sequence[] args, Sequence contextSequence)
      throws XPathException {
    final Sequence seq = args[0];
    Sequence tmp;
    if (seq.isEmpty()) {
      tmp = Sequence.EMPTY_SEQUENCE;
    } else if (isCalledAs("head")) {
      tmp = seq.itemAt(0).toSequence();
    } else {
            if (seq instanceof NodeSet) {
                tmp = new ExtArrayNodeSet();
                ((ExtArrayNodeSet)tmp).keepUnOrdered(unordered);
            } else {
                tmp = new ValueSequence();
                ((ValueSequence)tmp).keepUnOrdered(unordered);
            }
           
           
            tmp = seq.tail();
    }
    return tmp;
  }

}
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