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//
// C++ Interface: history
//
// Description:
//
//
// Author: Benjamin Mesing <bensmail@gmx.net>, (C) 2004
//
// Copyright: See COPYING file that comes with this distribution
//
//
#ifndef __HISTORY_H_2004_04_18
#define __HISTORY_H_2004_04_18
#include <list>
using namespace std;
namespace NBrowser {
/** The history is characterized by a list of entries and a current position. In this it is similar to the
* ADT table.
* @invariant _entries.empty() -> _current.end()
* @author Benjamin Mesing
*/
template <typename T>
class History
{
typedef list<T> Entries;
Entries _entries;
typename list<T>::iterator _current;
public:
History();
/** @returns if forward is possible i.e. we are not at the end of the history.
* @todo is --end() valid??*/
bool forwardPossible() const { return !_entries.empty() && (_current != (--_entries.end())); };
/** @returns if back is possible i.e. we are not at the start of the history. */
bool backPossible() const { return !_entries.empty() && (_current!=_entries.begin()); };
/** Make the next recent entry the current one and returns it.
* @pre forward must be possible */
const T& forward() { return *(++_current); };
/** Make the last recent entry the current one and returns it.
* @pre back must be possible */
const T& back() { return *(--_current); };
/** @brief Returns the current entry which <b>must</b> exist.
*
* @pre empty() != 0
*/
const T& current() const { return *_current; }
/** @brief Returns if the history is empty. */
bool empty() const { return _entries.empty(); }
/** @brief Appends an entry after the current position.
*
* If the current position is not the last one, all
* following entries will be removed. The current entry will be the one appended. */
void append(const T& t);
/** Clears the history. */
void clear();
};
template <typename T>
History<T>::History()
{
_current = _entries.end();
}
template <typename T>
void History<T>::append(const T& t)
{
if (_current != _entries.end())
{ // delete all entries after the current one
_entries.erase(++_current, _entries.end());
}
_current = _entries.insert(_entries.end(), t);
}
template <typename T>
void History<T>::clear()
{
_entries.clear();
_current=_entries.end();
}
};
#endif // __HISTORY_H_2004_04_18
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