81 lines
2.7 KiB
C++
81 lines
2.7 KiB
C++
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/*
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RATIONAL.hpp - support for precise rational arithmetics
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Copyright (C) Lumiera.org
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2022, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file rational.hpp
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** Rational number support, based on `boost::rational`.
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** As an extension to integral arithmetics, rational numbers can be defined
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** as a pair (numerator, denominator); since most calculations imply multiplication
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** by common factors, each calculation will be followed by normalisation to greatest
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** common denominator, to keep numbers within value range. Obviously, this incurs
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** a significant performance penalty — while on the other hand allowing for lossless
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** computations on fractional scales, which can be notoriously difficult to handle
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** with floating point numbers. The primary motivation for using this number format
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** is for handling fractional time values properly, e.g 1/30 sec or 1/44100 sec.
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**
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** The underlying implementation from boost::rational can be parametrised with various
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** integral data types; since our time handling is based on 64bit integers, we mainly
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** use the specialisation `boost::rational<int64_t>`.
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**
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** @note all compatible integral types can be automatically converted to rational
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** numbers, which is a lossless conversion. The opposite is not true: to get
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** a "ordinary" number — be it integral or floating point — an explicit
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** conversion using `rational_cast<NUM> (fraction)` is necessary, which
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** performs the division of `numerator/denominator` in the target value domain.
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**
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** @see zoom-window.hpp
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** @see timevalue.hpp
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*/
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#ifndef LIB_RATIONAL_H
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#define LIB_RATIONAL_H
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#include <stdint.h>
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#include <boost/rational.hpp>
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namespace util {
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using Rat = boost::rational<int64_t>;
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using boost::rational_cast;
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} // namespace util
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/**
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* user defined literal for constant rational numbers.
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* \code
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* Rat twoThirds = 2_r/3;
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* \endcode
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*/
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inline util::Rat
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operator""_r (unsigned long long num)
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{
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return util::Rat{num};
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}
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#endif /*LIB_RATIONAL_H*/
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