58 lines
2.0 KiB
Plaintext
58 lines
2.0 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:gmp_rational gmp_rational]
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`#include <boost/multiprecision/gmp.hpp>`
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namespace boost{ namespace multiprecision{
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class gmp_rational;
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typedef number<gmp_rational > mpq_rational;
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}} // namespaces
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The `gmp_rational` back-end is used via the typedef `boost::multiprecision::mpq_rational`. It acts as a thin wrapper around the [gmp] `mpq_t`
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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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As well as the usual conversions from arithmetic and string types, instances of `number<gmp_rational>` are copy constructible
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and assignable from:
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* The [gmp] native types: `mpz_t`, `mpq_t`.
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* `number<gmp_int>`.
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There is also a two-argument constructor that accepts a numerator and denominator (both of type `number<gmp_int>`).
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There are also non-member functions:
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mpz_int numerator(const mpq_rational&);
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mpz_int denominator(const mpq_rational&);
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which return the numerator and denominator of the number.
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It's also possible to access the underlying `mpq_t` via the `data()` member function of `mpq_rational`.
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Things you should know when using this type:
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* Default constructed `mpq_rational`s have the value zero (this is the [gmp] default 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 the [gmp] library's global settings, so this type can coexist with existing
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[gmp] code.
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* The code can equally be used with [mpir] as the underlying library - indeed that is the preferred option on Win32.
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[h5 Example:]
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[mpq_eg]
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[endsect] [/section:gmp_rational gmp_rational]
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