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/* Copyright (c) 1997-2024
Ewgenij Gawrilow, Michael Joswig, and the polymake team
Technische Universität Berlin, Germany
https://polymake.org
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version: http://www.gnu.org/licenses/gpl.txt.
This program 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 General Public License for more details.
--------------------------------------------------------------------------------
*/
#pragma once
#include "polymake/internal/iterators.h"
#include "polymake/perl/constants.h"
#include "polymake/perl/Value.h"
#include "polymake/optional"
namespace pm { namespace perl {
template <typename Container, bool _simple=check_iterator_feature<typename container_traits<Container>::iterator, end_sensitive>::value>
class element_finder_helper {
protected:
typename container_traits<Container>::iterator pos;
public:
element_finder_helper(Container&, typename container_traits<Container>::iterator where)
: pos(where) {}
};
template <typename Container>
class element_finder_helper<Container, false> {
protected:
typename ensure_features<Container, end_sensitive>::iterator pos;
public:
element_finder_helper(Container& c, typename container_traits<Container>::iterator where)
: pos(entire(c)) { pos=where; }
};
template <typename Container>
class element_finder
: protected element_finder_helper<const Container> {
public:
template <typename Key>
element_finder(const Container& c, const Key& key)
: element_finder_helper<const Container>(c, c.find(key)) {}
explicit operator bool() const noexcept { return !this->pos.at_end(); }
const auto& value() const { return this->pos->second; }
};
template <typename Container>
struct is_optional_value<element_finder<Container>>
: std::true_type {};
template <typename Container, typename Key>
element_finder<Container> find_element(const Container& c, const Key& key)
{
return element_finder<Container>(c, key);
}
template <typename Container>
class delayed_eraser
: protected element_finder_helper<Container> {
public:
template <typename Key>
delayed_eraser(Container& c_arg, const Key& key)
: element_finder_helper<Container>(c_arg, c_arg.find(key))
, c(c_arg) {}
explicit operator bool() const noexcept { return !this->pos.at_end(); }
decltype(auto) value() const { return std::move(this->pos->second); }
~delayed_eraser()
{
if (operator bool()) c.erase(this->pos);
}
private:
Container& c;
};
template <typename Container>
struct is_optional_value<delayed_eraser<Container>>
: std::true_type {};
template <typename Container, typename Key>
delayed_eraser<Container> delayed_erase(Container& c, const Key& key)
{
return delayed_eraser<Container>(c, key);
}
} }
// Local Variables:
// mode:C++
// c-basic-offset:3
// indent-tabs-mode:nil
// End:
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