[/
  Copyright 2021 - 2025 Fahad Syed.
  Copyright 2025 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:cpp_double_fp_ref cpp_double_fp_backend]

   namespace boost{ namespace multiprecision {

   template <class FloatingPointType>
   class cpp_double_fp_backend;

   typedef number<cpp_double_fp_backend<float>, et_off> cpp_double_float;
   typedef number<cpp_double_fp_backend<double>, et_off> cpp_double_double;
   typedef number<cpp_double_fp_backend<long double>, et_off> cpp_double_long_double;
   typedef number<cpp_double_fp_backend<boost::float128_type>, et_off> cpp_double_float128; // Only when boost::float128_type is available

   }} // namespaces

The `cpp_double_fp_backend` back-end is the sum of two IEEE floating-point numbers
combined to create a type having roughly twice the composite width of one of its parts.
The `cpp_double_fp_backend` back-end is used in conjunction with `number`
and acts as an entirely C++ header only floating-point number type.

Class template `cpp_double_fp_backend` fulfills all of the requirements for a [link boost_multiprecision.ref.backendconc Backend] type.
Its members and non-member functions are deliberately not documented: these are considered implementation details that are subject
to change.

The class takes one template parameter:

[variablelist
[[FloatingPointType][The constituent IEEE floating-point value of the two limbs of the composite type.
This can be `float`, `double`, `long double` or when available `boost::float128_type`.]]
]

The type of `number_category<cpp_dec_float<Args...> >::type` is `std::integral_constant<int, number_kind_floating_point>`.

More information on this type can be found in the [link boost_multiprecision.tut.floats.cpp_double_fp_backend tutorial].

[endsect]