...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
#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:
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:
mpq_rational
s
have the value zero (this is the GMP
default behavior).
std::overflow_error
being thrown.
std::runtime_error
being thrown if the string can not be interpreted as a valid rational
number.
#include <boost/multiprecision/gmp.hpp> using namespace boost::multiprecision; mpq_rational v = 1; // Do some arithmetic: for(unsigned i = 1; i <= 1000; ++i) v *= i; v /= 10; std::cout << v << std::endl; // prints 1000! / 10 std::cout << numerator(v) << std::endl; std::cout << denominator(v) << std::endl; mpq_rational w(2, 3); // component wise constructor std::cout << w << std::endl; // prints 2/3 // Access the underlying data: mpq_t q; mpq_init(q); mpq_set(q, v.backend().data());