forked from mpusz/mp-units
215 lines
8.5 KiB
C++
215 lines
8.5 KiB
C++
// The MIT License (MIT)
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//
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// Copyright (c) 2018 Mateusz Pusz
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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#pragma once
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#include <units/bits/derived_symbol_text.h>
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#include <units/bits/external/downcasting.h>
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// IWYU pragma: begin_exports
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#include <units/bits/derived_unit.h>
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#include <units/bits/external/fixed_string.h>
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#include <units/prefix.h>
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#include <units/ratio.h>
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#include <units/symbol_text.h>
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// IWYU pragma: end_exports
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namespace units {
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/**
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* @brief A common point for a hierarchy of units
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*
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* A unit is an entity defined and adopted by convention, with which any other quantity of
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* the same kind can be compared to express the ratio of the second quantity to the first
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* one as a number.
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*
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* All units of the same dimension can be convereted between each other. To allow this all of
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* them are expressed as different ratios of the same one proprietary chosen reference unit
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* (i.e. all length units are expressed in terms of meter, all mass units are expressed in
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* terms of gram, ...)
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*
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* @tparam R a ratio of a reference unit
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* @tparam U a unit to use as a reference for this dimension
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*/
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template<ratio R, typename U>
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requires UnitRatio<R>
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struct scaled_unit : downcast_base<scaled_unit<R, U>> {
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static constexpr ::units::ratio ratio = R;
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using reference = U;
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};
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template<Dimension D, auto R>
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// template<Dimension D, ratio R> // TODO: GCC crash!!!
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requires UnitRatio<R>
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using downcast_unit = downcast<scaled_unit<R, typename dimension_unit<D>::reference>>;
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template<Unit U1, Unit U2>
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struct same_unit_reference : is_same<typename U1::reference, typename U2::reference> {};
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/**
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* @brief An unnamed unit
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*
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* Defines a new unnamed (in most cases coherent) derived unit of a specific derived dimension
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* and it should be passed in this dimension's definition.
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*
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* @tparam Child inherited class type used by the downcasting facility (CRTP Idiom)
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*/
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template<typename Child>
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struct unit : downcast_dispatch<Child, scaled_unit<ratio(1), Child>> {
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static constexpr bool is_named = false;
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using prefix_family = no_prefix;
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};
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/**
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* @brief A named unit
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*
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* Defines a named (in most cases coherent) unit that is then passed to a dimension definition.
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* A named unit may be used by other units defined with the prefix of the same type, unless
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* no_prefix is provided for PF template parameter (in such a case it is impossible to define
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* a prefix unit based on this one).
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*
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* @tparam Child inherited class type used by the downcasting facility (CRTP Idiom)
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* @tparam Symbol a short text representation of the unit
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* @tparam PF no_prefix or a type of prefix family
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*/
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template<typename Child, basic_symbol_text Symbol, PrefixFamily PF>
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struct named_unit : downcast_dispatch<Child, scaled_unit<ratio(1), Child>> {
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static constexpr bool is_named = true;
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static constexpr auto symbol = Symbol;
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using prefix_family = PF;
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};
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/**
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* @brief A scaled unit
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*
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* Defines a new named unit that is a scaled version of another unit. Such unit can be used by
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* other units defined with the prefix of the same type, unless no_prefix is provided for PF
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* template parameter (in such a case it is impossible to define a prefix unit based on this
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* one).
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*
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* @tparam Child inherited class type used by the downcasting facility (CRTP Idiom)
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* @tparam Symbol a short text representation of the unit
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* @tparam PF no_prefix or a type of prefix family
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* @tparam R a scale to apply to U
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* @tparam U a reference unit to scale
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*/
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template<typename Child, basic_symbol_text Symbol, PrefixFamily PF, ratio R, Unit U>
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requires UnitRatio<R>
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struct named_scaled_unit : downcast_dispatch<Child, scaled_unit<R * U::ratio, typename U::reference>> {
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static constexpr bool is_named = true;
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static constexpr auto symbol = Symbol;
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using prefix_family = PF;
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};
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/**
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* @brief A prefixed unit
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*
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* Defines a new unit that is a scaled version of another unit by the provided prefix. It is
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* only possible to create such a unit if the given prefix type matches the one defined in a
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* reference unit.
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*
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* @tparam Child inherited class type used by the downcasting facility (CRTP Idiom)
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* @tparam P prefix to be appied to the reference unit
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* @tparam U reference unit
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*/
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template<typename Child, Prefix P, Unit U>
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requires U::is_named && std::same_as<typename P::prefix_family, typename U::prefix_family>
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struct prefixed_unit : downcast_dispatch<Child, scaled_unit<P::ratio * U::ratio, typename U::reference>> {
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static constexpr bool is_named = true;
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static constexpr auto symbol = P::symbol + U::symbol;
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using prefix_family = no_prefix;
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};
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/**
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* @brief A unit with a deduced ratio and symbol
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*
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* Defines a new unit with a deduced ratio and symbol based on the recipe from the provided
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* derived dimension. The number and order of provided units should match the recipe of the
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* derived dimension. All of the units provided should also be a named ones so it is possible
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* to create a deduced symbol text.
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*
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* @tparam Child inherited class type used by the downcasting facility (CRTP Idiom)
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* @tparam Dim a derived dimension recipe to use for deduction
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* @tparam U the unit of the first composite dimension from provided derived dimension's recipe
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* @tparam URest the units for the rest of dimensions from the recipe
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*/
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template<typename Child, DerivedDimension Dim, Unit U, Unit... URest>
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requires detail::same_scaled_units<typename Dim::recipe, U, URest...> &&
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(U::is_named && (URest::is_named && ... && true))
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struct derived_unit : downcast_dispatch<Child, detail::derived_unit<Dim, U, URest...>> {
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static constexpr bool is_named = false;
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static constexpr auto symbol = detail::derived_symbol_text<Dim, U, URest...>();
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using prefix_family = no_prefix;
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};
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/**
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* @brief An aliased named unit
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*
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* Defines a named alias for another unit. It is useful to assign alternative names and symbols
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* to the already predefined units (i.e. "tonne" for "megagram").
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* An alias unit may be used by other units defined with the prefix of the same type, unless
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* no_prefix is provided for PF template parameter (in such a case it is impossible to define
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* a prefix unit based on this one).
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*
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* @tparam U Unit for which an alias is defined
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* @tparam Symbol a short text representation of the unit
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* @tparam PF no_prefix or a type of prefix family
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*/
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template<Unit U, basic_symbol_text Symbol, PrefixFamily PF>
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struct alias_unit : U {
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static constexpr bool is_named = true;
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static constexpr auto symbol = Symbol;
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using prefix_family = PF;
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};
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/**
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* @brief A prefixed alias unit
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*
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* Defines a new unit that is an alias for a scaled version of another unit by the provided
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* prefix. It is only possible to create such a unit if the given prefix type matches the one
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* defined in a reference unit.
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*
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* @tparam U Unit for which an alias is defined
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* @tparam P prefix to be appied to the reference unit
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* @tparam AU reference alias unit
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*/
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// TODO gcc bug: 95015
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// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95015
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// template<Unit U, Prefix P, AliasUnit AU>
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// requires (!AliasUnit<U>) && std::same_as<typename P::prefix_family, typename AU::prefix_family>
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template<Unit U, Prefix P, Unit AU>
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requires AU::is_named && std::same_as<typename P::prefix_family, typename AU::prefix_family>
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struct prefixed_alias_unit : U {
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static constexpr bool is_named = true;
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static constexpr auto symbol = P::symbol + AU::symbol;
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using prefix_family = no_prefix;
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};
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/**
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* @brief Unknown unit
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*
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* Used as a coherent unit of an unknown dimension.
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*/
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struct unknown_coherent_unit : unit<unknown_coherent_unit> {};
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} // namespace units
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