96 lines
3.6 KiB
C++
96 lines
3.6 KiB
C++
/** @file Quantity2.hpp
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*
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* Author: Roland Conybeare
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**/
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#pragma once
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#include "quantity2_concept.hpp"
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#include "scaled_unit2.hpp"
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#include "natural_unit.hpp"
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namespace xo {
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namespace qty {
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/** @class quantity
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* @brief represent a scalar quantity with attached units. enforce dimensional consistency.
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*
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* Constexpr implementation, but units are explicitly represented:
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* sizeof(Quantity2) > sizeof(Repr)
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*
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* Explicit unit representation allows introducing units at runtime,
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* for example in python bindings
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*
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* Require:
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* - Repr supports numeric operations (+, -, *, /)
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* - Repr supports conversion from double.
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**/
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template <typename Repr = double,
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typename Int = std::int64_t>
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class Quantity2 {
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public:
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using repr_type = Repr;
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using unit_type = natural_unit<Int>;
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using ratio_int_type = Int;
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public:
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constexpr Quantity2(Repr scale,
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const natural_unit<Int> & unit)
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: scale_{scale}, unit_{unit} {}
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constexpr const repr_type & scale() const { return scale_; }
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constexpr const unit_type & unit() const { return unit_; }
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constexpr Quantity2 unit_qty() const { return Quantity2(1, unit_); }
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constexpr Quantity2 reciprocal() const { return Quantity2(1.0 / scale_, unit_.reciprocal()); }
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template <typename OtherQuantity>
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static constexpr
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auto multiply(const Quantity2 & x, const OtherQuantity & y) {
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using r_repr_type = std::common_type_t<typename Quantity2::repr_type,
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typename OtherQuantity::repr_type>;
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using r_int_type = std::common_type_t<typename Quantity2::ratio_int_type,
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typename OtherQuantity::ratio_int_type>;
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auto rr = detail::nu_product(x.unit(), y.unit());
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r_repr_type r_scale = (::sqrt(rr.outer_scale_sq_)
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* rr.outer_scale_exact_.template to<r_repr_type>()
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* static_cast<r_repr_type>(x.scale())
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* static_cast<r_repr_type>(y.scale()));
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return Quantity2<r_repr_type, r_int_type>(r_scale,
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rr.natural_unit_);
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}
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private:
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/** @brief quantity represents this multiple of a unit amount **/
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Repr scale_ = Repr{};
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/** @brief unit for this quantity **/
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natural_unit<Int> unit_;
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}; /*Quantity2*/
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/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
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**/
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template <typename Repr = double,
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typename Int = std::int64_t>
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inline constexpr Quantity2<Repr, Int>
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unit_qty(const scaled_unit2<Int> & u) {
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return Quantity2<Repr, Int>
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(u.outer_scale_exact_.template to<double>() * ::sqrt(u.outer_scale_sq_),
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u.natural_unit_);
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}
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/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
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**/
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template <typename Quantity, typename OtherQuantity>
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constexpr auto
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operator* (const Quantity & x, const OtherQuantity & y)
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{
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return Quantity::multiply(x, y);
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}
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} /*namespace qty*/
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} /*namespace xo*/
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/** end Quantity2.hpp **/
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