[/ Copyright 2011 - 2020 John Maddock. Copyright 2013 - 2019 Paul A. Bristow. Copyright 2013 Christopher Kormanyos. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt). ] [section:gmp_rational gmp_rational] `#include <boost/multiprecision/gmp.hpp>` namespace boost{ namespace multiprecision{ class gmp_rational; typedef number<gmp_rational > mpq_rational; }} // namespaces 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` to provide a rational number type that is a drop-in replacement for the native C++ number types, but with unlimited precision. As well as the usual conversions from arithmetic and string types, instances of `number<gmp_rational>` are copy constructible and assignable from: * The [gmp] native types: `mpz_t`, `mpq_t`. * `number<gmp_int>`. There is also a two-argument constructor that accepts a numerator and denominator (both of type `number<gmp_int>`). There are also non-member functions: mpz_int numerator(const mpq_rational&); mpz_int denominator(const mpq_rational&); which return the numerator and denominator of the number. It's also possible to access the underlying `mpq_t` via the `data()` member function of `mpq_rational`. Things you should know when using this type: * Default constructed `mpq_rational`s have the value zero (this is the [gmp] default behavior). * Division by zero results in a `std::overflow_error` being thrown. * Conversion from a string results in a `std::runtime_error` being thrown if the string can not be interpreted as a valid rational number. * No changes are made to the [gmp] library's global settings, so this type can coexist with existing [gmp] code. * The code can equally be used with [mpir] as the underlying library - indeed that is the preferred option on Win32. [h5 Example:] [mpq_eg] [endsect] [/section:gmp_rational gmp_rational]