DataStack.cs

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#region License
/* **********************************************************************************
 * Copyright (c) Roman Ivantsov
 * This source code is subject to terms and conditions of the MIT License
 * for Irony. A copy of the license can be found in the License.txt file
 * at the root of this distribution. 
 * By using this source code in any fashion, you are agreeing to be bound by the terms of the 
 * MIT License.
 * You must not remove this notice from this software.
 * **********************************************************************************/
#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Irony.Interpreter {
  public class DataStack { 

    List<object> _data = new List<object>(16);
    object _lastPushedItem;
    object _unassigned; //Unassigned singleton value

    public void Init(object unassigned) {
      _unassigned = unassigned;
      _lastPushedItem = unassigned;
      _data.Clear(); 
    }

    public int Count {
      get {return _data.Count;}
    }
    public object this[int index] {
      get {return _data[_data.Count - 1 - index]; }
    }
    public object Top {
      get { return _data[_data.Count - 1]; }
    }
    public object Pop() {
      if (Count == 0)
        throw new Exception(Resources.ErrInternalErrDataPopFailed); 
      var result = Top;
      _data.RemoveAt(_data.Count - 1);
      return result; 
    }
    public void Pop(int count) {
      _data.RemoveRange(_data.Count - count, count);
    }
    public void PopUntil(int toCount) {
      if (toCount >= _data.Count) return;
      Pop(_data.Count - toCount); 
    }
    public void Push(object item) {
      _lastPushedItem = item; 
      _data.Add(item);
    }
    public void Replace(int removeCount, object item) {
      Pop(removeCount);
      Push(item); 
    }
    public object LastPushedItem {
      get { return _lastPushedItem; }
    }
    public override string ToString() {
      return this.GetType().Name + "(Count=" + Count + ")";
    }

  }//class
}//namespace