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[/
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:internals Internal Support Code]
There are some traits classes which authors of new backends should be aware of:
namespace boost{ namespace multiprecision{ namespace detail{
template<typename From, typename To>
struct is_explicitly_convertible;
}}}
Inherits from `std::integral_constant<bool,true>` if type `From` has an explicit conversion from `To`.
template <class From, class To>
struct is_lossy_conversion
{
static const bool value = see below;
};
Member `value` is true if the conversion from `From` to `To` would result in a loss of precision, and `false` otherwise.
The default version of this trait simply checks whether the ['kind] of conversion (for example from a floating-point to an integer type)
is inherently lossy. Note that if either of the types `From` or `To` are of an unknown number category (because `number_category` is not
specialised for that type) then this trait will be `true`.
template<typename From, typename To>
struct is_restricted_conversion
{
static const bool value = see below;
};
Member `value` is `true` if `From` is only explicitly convertible to `To` and not implicitly convertible, or
if `is_lossy_conversion<From, To>::value` is `true`. Otherwise `false`.
Note that while this trait is the ultimate arbiter of which constructors are marked as `explicit` in class `number`,
authors of backend types should generally specialise one of the traits above, rather than this one directly.
template <class T>
is_signed_number;
template <class T>
is_unsigned_number;
These two traits inherit from either `std::integral_constant<bool, true>` or `std::integral_constant<bool, false>`, by default types are assumed to be signed unless
`is_unsigned_number` is specialized for that type.
[endsect]
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