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// -*- c++ -*-
// Copyright 1998,1999 Zanshin Inc. <http://www.zanshin.com/>
// The contents of this file are subject to the Zanshin Public License Version
// 1.0 (the "License"); you may not use this file except in compliance with the
// License. You should have received a copy of the License with Latte; see
// the file COPYING. You may also obtain a copy of the License at
// <http://www.zanshin.com/ZPL.html>.
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
// for the specific language governing rights and limitations under the
// License.
//
// The Original Code is Latte.
//
// The Initial Developer of the Original Code is Zanshin, Inc.
#ifndef LATTE_MEMO_H
# define LATTE_MEMO_H
// Horrors, a global! I'd use a namespace to contain this, if namespaces were
// more widely implemented.
extern unsigned int g_memo_last_reset;
template <class T, class F>
class memo {
public:
memo(const F &fn) : m_known(0), m_fn(fn) {}
T &val() {
if (m_known >= g_memo_last_reset)
return m_val;
m_known = g_memo_last_reset;
return ((m_val = m_fn()));
}
const T &val() const {
if (m_known >= g_memo_last_reset)
return m_val;
mutate(m_known) = g_memo_last_reset;
return ((mutate(m_val) = m_fn()));
}
void reset() { m_known = 0; }
static void reset_all() { ++g_memo_last_reset; }
private:
mutable unsigned int m_known;
mutable T m_val;
F m_fn;
};
#endif // LATTE_MEMO_H
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