001    /**
002     * =========================================
003     * LibFormula : a free Java formula library
004     * =========================================
005     *
006     * Project Info:  http://reporting.pentaho.org/libformula/
007     *
008     * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors.
009     *
010     * This library is free software; you can redistribute it and/or modify it under the terms
011     * of the GNU Lesser General Public License as published by the Free Software Foundation;
012     * either version 2.1 of the License, or (at your option) any later version.
013     *
014     * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
015     * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
016     * See the GNU Lesser General Public License for more details.
017     *
018     * You should have received a copy of the GNU Lesser General Public License along with this
019     * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
020     * Boston, MA 02111-1307, USA.
021     *
022     * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
023     * in the United States and other countries.]
024     *
025     *
026     * ------------
027     * $Id: ConcatOperator.java 2887 2007-06-06 17:07:52Z taqua $
028     * ------------
029     * (C) Copyright 2006-2007, by Pentaho Corporation.
030     */
031    package org.jfree.formula.operators;
032    
033    import org.jfree.formula.EvaluationException;
034    import org.jfree.formula.FormulaContext;
035    import org.jfree.formula.LibFormulaErrorValue;
036    import org.jfree.formula.lvalues.TypeValuePair;
037    import org.jfree.formula.typing.TypeRegistry;
038    import org.jfree.formula.typing.coretypes.TextType;
039    
040    /**
041     * Concats two strings operator.
042     *
043     * @author Thomas Morgner
044     */
045    public class ConcatOperator implements InfixOperator
046    {
047      public ConcatOperator()
048      {
049      }
050    
051      public TypeValuePair evaluate(final FormulaContext context,
052                                    final TypeValuePair value1,
053                                    final TypeValuePair value2)
054          throws EvaluationException
055      {
056        final TypeRegistry typeRegistry = context.getTypeRegistry();
057    
058        // Error or empty string, that's the question ..
059        final Object raw1 = value1.getValue();
060        final Object raw2 = value2.getValue();
061        if (raw1 == null || raw2 == null)
062        {
063          throw new EvaluationException(LibFormulaErrorValue.ERROR_NA_VALUE);
064        }
065    
066        final String text1 = typeRegistry.convertToText(value1.getType(), raw1);
067        final String text2 = typeRegistry.convertToText(value2.getType(), raw2);
068        if (text1 == null && text2 == null)
069        {
070          throw new EvaluationException
071              (LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
072        }
073        if (text1 == null)
074        {
075          return new TypeValuePair(TextType.TYPE, text2);
076        }
077        if (text2 == null)
078        {
079          return new TypeValuePair(TextType.TYPE, text1);
080        }
081    
082        return new TypeValuePair(TextType.TYPE, text1 + text2);
083      }
084    
085      public int getLevel()
086      {
087        return 300;
088      }
089    
090    
091      public String toString()
092      {
093        return "&";
094      }
095    
096      public boolean isLeftOperation()
097      {
098        return true;
099      }
100    
101      /**
102       * Defines, whether the operation is associative. For associative operations,
103       * the evaluation order does not matter, if the operation appears more than
104       * once in an expression, and therefore we can optimize them a lot better than
105       * non-associative operations (ie. merge constant parts and precompute them
106       * once).
107       *
108       * @return true, if the operation is associative, false otherwise
109       */
110      public boolean isAssociative()
111      {
112        return false;
113      }
114    
115    }