51 lines
1.9 KiB
Plaintext
51 lines
1.9 KiB
Plaintext
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Copyright 2011 - 2020 John Maddock.
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Copyright 2013 - 2019 Paul A. Bristow.
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Copyright 2013 Christopher Kormanyos.
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt).
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]
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[section:tommath_rational tommath_rational]
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`#include <boost/multiprecision/tommath.hpp>`
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namespace boost{ namespace multiprecision{
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typedef rational_adpater<tommath_int> tommath_rational;
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typedef number<tommath_rational > tom_rational;
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}} // namespaces
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The `tommath_rational` back-end is used via the typedef `boost::multiprecision::tom_rational`. It acts as a thin wrapper around
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`boost::rational<tom_int>`
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to provide a rational number type that is a drop-in replacement for the native C++ number types, but with unlimited precision.
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The advantage of using this type rather than `boost::rational<tom_int>` directly, is that it is expression-template enabled,
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greatly reducing the number of temporaries created in complex expressions.
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There are also non-member functions:
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tom_int numerator(const tom_rational&);
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tom_int denominator(const tom_rational&);
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which return the numerator and denominator of the number.
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Things you should know when using this type:
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* Default constructed `tom_rational`s have the value zero (this the inherited Boost.Rational behavior).
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* Division by zero results in a `std::overflow_error` being thrown.
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* Conversion from a string results in a `std::runtime_error` being thrown if the string can not be
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interpreted as a valid rational number.
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* No changes are made to [tommath]'s global state, so this type can safely coexist with other [tommath] code.
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* Performance of this type has been found to be pretty poor - this need further investigation - but it appears that Boost.Rational
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needs some improvement in this area.
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[h5 Example:]
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[mp_rat_eg]
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[endsect] [/section:tommath_rational tommath_rational]
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