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//
// System.CharEnumerator.cs
//
// Author: Duncan Mak (duncan@ximian.com)
//
// (C) Ximian, Inc.
//
using System.Collections;
namespace System
{
[Serializable]
public sealed class CharEnumerator : IEnumerator, ICloneable
{
private string str;
private int index;
private int length;
// Representation invariant:
// length == str.Length
// -1 <= index <= length
// Constructor
internal CharEnumerator (string s)
{
str = s;
index = -1;
length = s.Length;
}
// Property
public char Current
{
get {
if (index == -1 || index == length)
throw new InvalidOperationException
("The position is not valid.");
return str [index];
}
}
object IEnumerator.Current
{
get {
if (index == -1 || index == length)
throw new InvalidOperationException
("The position is not valid");
return str [index];
}
}
// Methods
public object Clone ()
{
CharEnumerator x = new CharEnumerator (str);
x.index = index;
return x;
}
public bool MoveNext ()
{
// Representation invariant holds: -1 <= index <= length
index ++;
// Now: 0 <= index <= length+1;
// <=>
// 0 <= index < length (OK) ||
// length <= index <= length+1 (Out of bounds)
if (index >= length) {
index = length;
// Invariant restored:
// length == index
// =>
// -1 <= index <= length
return false;
}
else
return true;
}
public void Reset ()
{
index = -1;
}
}
}
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