source: stable/HeuristicLab.ExtLibs/HeuristicLab.EPPlus/4.0.3/EPPlus-4.0.3/FormulaParsing/ExpressionGraph/ExpressionGraph.cs

/*******************************************************************************
 * You may amend and distribute as you like, but don't remove this header!
 *
 * EPPlus provides server-side generation of Excel 2007/2010 spreadsheets.
 * See http://www.codeplex.com/EPPlus for details.
 *
 * Copyright (C) 2011  Jan Källman
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.

 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  
 * See the GNU Lesser General Public License for more details.
 *
 * The GNU Lesser General Public License can be viewed at http://www.opensource.org/licenses/lgpl-license.php
 * If you unfamiliar with this license or have questions about it, here is an http://www.gnu.org/licenses/gpl-faq.html
 *
 * All code and executables are provided "as is" with no warranty either express or implied. 
 * The author accepts no liability for any damage or loss of business that this product may cause.
 *
 * Code change notes:
 * 
 * Author             Change            Date
 * ******************************************************************************
 * Mats Alm                       Added                   2013-03-01 (Prior file history on https://github.com/swmal/ExcelFormulaParser)
 *******************************************************************************/
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace OfficeOpenXml.FormulaParsing.ExpressionGraph
{
    public class ExpressionGraph
    {
        private List<Expression> _expressions = new List<Expression>();
        public IEnumerable<Expression> Expressions { get { return _expressions; } }
        public Expression Current { get; private set; }

        public Expression Add(Expression expression)
        {
            _expressions.Add(expression);
            if (Current != null)
            {
                Current.Next = expression;
                expression.Prev = Current;
            }
            Current = expression;
            return expression;
        }

        public void Reset()
        {
            _expressions.Clear();
            Current = null;
        }

        public void Remove(Expression item)
        {
            if (item == Current)
            {
                Current = item.Prev ?? item.Next;
            }
            _expressions.Remove(item);
        }
    }
}