Ichthyostega
806db414dd
* Lumiera source code always was copyrighted by individual contributors * there is no entity "Lumiera.org" which holds any copyrights * Lumiera source code is provided under the GPL Version 2+ == Explanations == Lumiera as a whole is distributed under Copyleft, GNU General Public License Version 2 or above. For this to become legally effective, the ''File COPYING in the root directory is sufficient.'' The licensing header in each file is not strictly necessary, yet considered good practice; attaching a licence notice increases the likeliness that this information is retained in case someone extracts individual code files. However, it is not by the presence of some text, that legally binding licensing terms become effective; rather the fact matters that a given piece of code was provably copyrighted and published under a license. Even reformatting the code, renaming some variables or deleting parts of the code will not alter this legal situation, but rather creates a derivative work, which is likewise covered by the GPL! The most relevant information in the file header is the notice regarding the time of the first individual copyright claim. By virtue of this initial copyright, the first author is entitled to choose the terms of licensing. All further modifications are permitted and covered by the License. The specific wording or format of the copyright header is not legally relevant, as long as the intention to publish under the GPL remains clear. The extended wording was based on a recommendation by the FSF. It can be shortened, because the full terms of the license are provided alongside the distribution, in the file COPYING.
87 lines
2.8 KiB
C++
87 lines
2.8 KiB
C++
/*
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UTIL-TUPLE.hpp - helpers and convenience shortcuts for working with tuples
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Copyright (C)
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2023, Hermann Vosseler <Ichthyostega@web.de>
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**Lumiera** is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2 of the License, or (at your
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option) any later version. See the file COPYING for further details.
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*/
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/** @file util-tuples.hpp
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** Some small helpers and convenience shortcuts to simplify working with
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** tuples and sequences (given by iterator). While tuples and sequences
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** are fundamentally different insofar a tuple has a fixed structure (and
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** may hold elements of different type), sometimes it can be convenient to
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** treat a tuple like a sequence (especially a tuple holding elements of a
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** single type. Notably, an iterator can be unloaded into a fixed-size tuple,
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** which in turn can than be used in a structural binding to unpack references
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** to the elements into scoped variables. Obviously, the meaning of the elements
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** in the sequence must be fixed and predetermined -- which is often the case
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** when dealing with tests or communication protocols.
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**
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** @see util-tuple-test.cpp
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** @see util-coll.hpp
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**
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*/
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#ifndef UTIL_TUPLE_H
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#define UTIL_TUPLE_H
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#include <tuple>
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#include <utility>
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namespace util {
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namespace { // recursive builder helper to unpack a sequence...
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template<size_t N>
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using cnt_ = std::integral_constant<size_t, N>;
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template<class SEQ>
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inline auto
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_buildSeqTuple (cnt_<0>, SEQ&&)
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{
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return std::tuple<>{};
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}
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template<size_t N, class SEQ>
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inline auto
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_buildSeqTuple (cnt_<N>, SEQ&& iter)
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{
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auto prefixTuple = std::tie (*iter);
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++iter;
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return std::tuple_cat (prefixTuple, _buildSeqTuple (cnt_<N-1>{}, std::forward<SEQ> (iter)));
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}
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}//(End) unpacking helper
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/**
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* Unpack an iterator to build a fixed-size std::tuple of references
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* @tparam N (mandatory) defines the number of elements to unpack; can be zero
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* @param iter anything compliant to the Lumiera Forward Iterator protocol
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* @warning since the implementation uses `std::tie (*iter)`, a _reference_ is
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* stored, which may lead to strange and dangerous behaviour if the given
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* iterator exposes a reference to mutable internal state (e.g. "state core").
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* Moreover, it is assumed the iterator yields enough values to fill the new
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* tuple, and this is not checked; an empty or exhausted iterator might throw,
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* or yield otherwise undefined behaviour.
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*/
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template<size_t N, class SEQ>
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auto
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seqTuple (SEQ&& iter)
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{
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return _buildSeqTuple (cnt_<N>{}, std::forward<SEQ> (iter));
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}
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} // namespace util
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#endif /*UTIL_TUPLE_H*/
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