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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2025, Ben Burton *
* For further details contact Ben Burton (bab@debian.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 of the *
* License, or (at your option) any later version. *
* *
* As an exception, when this program is distributed through (i) the *
* App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or *
* (iii) Google Play by Google Inc., then that store may impose any *
* digital rights management, device limits and/or redistribution *
* restrictions that are required by its terms of service. *
* *
* 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. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program. If not, see <https://www.gnu.org/licenses/>. *
* *
**************************************************************************/
/*! \file link/data-impl.h
* \brief Contains implementation details for constructing knots and
* links from C++ initialiser lists.
*
* This file is automatically included from link.h; there is no need
* for end users to include it explicitly.
*/
#ifndef __REGINA_DATA_IMPL_H
#ifndef __DOXYGEN
#define __REGINA_DATA_IMPL_H
#endif
#include "utilities/exception.h"
namespace regina {
template <typename... Args>
Link Link::fromData(std::initializer_list<int> crossingSigns,
std::initializer_list<Args>... components) {
Link ans;
for (auto sign : crossingSigns) {
if (sign == 1 || sign == -1)
ans.crossings_.push_back(new Crossing(sign));
else
throw InvalidArgument("fromData(): crossing sign not ±1");
}
ans.addComponents(2 * crossingSigns.size(), components...);
return ans;
}
inline void Link::addComponents(size_t strandsRemaining) {
if (strandsRemaining != 0)
throw InvalidArgument("fromData(): too few strands");
}
template <typename... Args>
void Link::addComponents(size_t strandsRemaining,
std::initializer_list<int> component,
std::initializer_list<Args>... otherComponents) {
if (component.size() == 0) {
// Support an empty component via { }, though I suspect this is
// impossible to use because the C++ compiler cannot deduce the type.
components_.emplace_back();
} else if (component.size() == 1 && *component.begin() == 0) {
// Support an empty component via { 0 }.
// Here we increment strandsRemaining, to account for the extra
// integer (0) in our list that does not belong to any crossing.
components_.emplace_back();
++strandsRemaining;
} else {
size_t n = crossings_.size();
if constexpr (sizeof(int) <= sizeof(size_t)) {
if (n > static_cast<size_t>(INT_MAX))
throw InvalidArgument("fromData(): too many crossings "
"to hold using native C++ ints");
}
const int maxCrossing = static_cast<int>(n);
int tmpCross;
int tmpStrand;
auto it = component.begin();
if (*it == 0 || *it > maxCrossing || *it < -maxCrossing)
throw InvalidArgument("fromData(): crossing out of range");
if (*it > 0) {
tmpCross = *it;
tmpStrand = 1;
} else {
tmpCross = - *it;
tmpStrand = 0;
}
StrandRef curr, prev;
Crossing* cr = crossings_[tmpCross - 1];
curr = cr->strand(tmpStrand);
components_.push_back(curr);
for (++it; it != component.end(); ++it) {
prev = curr;
if (*it == 0 || *it > maxCrossing || *it < -maxCrossing)
throw InvalidArgument("fromData(): crossing out of range");
if (*it > 0) {
tmpCross = *it;
tmpStrand = 1;
} else {
tmpCross = - *it;
tmpStrand = 0;
}
cr = crossings_[tmpCross - 1];
curr = cr->strand(tmpStrand);
if (prev.crossing()->next_[prev.strand()])
throw InvalidArgument("fromData(): multiple passes "
"out of same strand of crossing");
prev.crossing()->next_[prev.strand()] = curr;
if (curr.crossing()->prev_[curr.strand()])
throw InvalidArgument("fromData(): multiple passes "
"into same strand of crossing");
curr.crossing()->prev_[curr.strand()] = prev;
}
prev = curr;
curr = components_.back();
if (prev.crossing()->next_[prev.strand()])
throw InvalidArgument("fromData(): multiple passes "
"out of same strand of crossing");
prev.crossing()->next_[prev.strand()] = curr;
if (curr.crossing()->prev_[curr.strand()])
throw InvalidArgument("fromData(): multiple passes "
"into same strand of crossing");
curr.crossing()->prev_[curr.strand()] = prev;
}
addComponents(strandsRemaining - component.size(), otherComponents...);
}
template <typename SignIterator, typename ComponentIterator>
Link Link::fromData(SignIterator beginSigns, SignIterator endSigns,
ComponentIterator beginComponents, ComponentIterator endComponents) {
using InputInt = std::remove_cv_t<std::remove_reference_t<
decltype(*beginComponents->begin())>>;
static_assert(std::is_integral_v<InputInt> &&
! std::is_unsigned_v<InputInt>, "fromData(): the iterator type "
"needs to dereference to give a native signed C++ integer type.");
Link ans;
for (auto sit = beginSigns; sit != endSigns; ++sit) {
if (*sit == 1 || *sit == -1)
ans.crossings_.push_back(new Crossing(*sit));
else
throw InvalidArgument("fromData(): crossing sign not ±1");
}
size_t strandsFound = 0;
size_t n = ans.crossings_.size();
if constexpr (sizeof(InputInt) <= sizeof(size_t)) {
if (n > static_cast<size_t>(std::numeric_limits<InputInt>::max()))
throw InvalidArgument("fromData(): too many crossings for "
"the given integer type");
}
const auto maxCrossing = static_cast<InputInt>(n);
for (auto cit = beginComponents; cit != endComponents; ++cit) {
if (cit->size() == 0) {
// Support an empty component via { }.
ans.components_.emplace_back();
} else if (cit->size() == 1 && *cit->begin() == 0) {
// Support an empty component via { 0 }.
ans.components_.emplace_back();
} else {
bool first = true;
StrandRef curr, prev;
for (auto c : *cit) {
if (c == 0 || c > maxCrossing || c < -maxCrossing)
throw InvalidArgument("fromData(): crossing out of range");
if (c > 0)
curr = ans.crossings_[c - 1]->upper();
else
curr = ans.crossings_[-(c + 1)]->lower();
if (first) {
ans.components_.push_back(curr);
first = false;
} else {
if (prev.crossing()->next_[prev.strand()])
throw InvalidArgument("fromData(): multiple passes "
"out of same strand of crossing");
prev.crossing()->next_[prev.strand()] = curr;
if (curr.crossing()->prev_[curr.strand()])
throw InvalidArgument("fromData(): multiple passes "
"into same strand of crossing");
curr.crossing()->prev_[curr.strand()] = prev;
}
prev = curr;
}
curr = ans.components_.back();
if (prev.crossing()->next_[prev.strand()])
throw InvalidArgument("fromData(): multiple passes "
"out of same strand of crossing");
prev.crossing()->next_[prev.strand()] = curr;
if (curr.crossing()->prev_[curr.strand()])
throw InvalidArgument("fromData(): multiple passes "
"into same strand of crossing");
curr.crossing()->prev_[curr.strand()] = prev;
strandsFound += cit->size();
}
}
if (strandsFound != 2 * ans.crossings_.size())
throw InvalidArgument("fromData(): incorrect number of strands");
return ans;
}
} // namespace regina
#endif
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