176 lines
7.4 KiB
C++
176 lines
7.4 KiB
C++
/** @file Quantity.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_unit.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 Quantity {
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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 Quantity(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 Quantity unit_qty() const { return Quantity(1, unit_); }
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constexpr Quantity reciprocal() const { return Quantity(1.0 / scale_, unit_.reciprocal()); }
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template <typename Quantity2>
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static constexpr
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auto multiply(const Quantity & x, const Quantity2 & y) {
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using r_repr_type = std::common_type_t<typename Quantity::repr_type,
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typename Quantity2::repr_type>;
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using r_int_type = std::common_type_t<typename Quantity::ratio_int_type,
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typename Quantity2::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 Quantity<r_repr_type, r_int_type>(r_scale,
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rr.natural_unit_);
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}
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template <typename Quantity2>
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static constexpr
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auto divide(const Quantity & x, const Quantity2 & y) {
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using r_repr_type = std::common_type_t<typename Quantity::repr_type,
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typename Quantity2::repr_type>;
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using r_int_type = std::common_type_t<typename Quantity::ratio_int_type,
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typename Quantity2::ratio_int_type>;
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auto rr = detail::nu_ratio(x.unit(), y.unit());
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/* note: nu_ratio() reports multiplicative outer scaling factors,
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* so multiply is correct here
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*/
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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 Quantity<r_repr_type, r_int_type>(r_scale,
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rr.natural_unit_);
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}
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template <typename Quantity2>
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static constexpr
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auto add(const Quantity & x, const Quantity2 & y) {
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using r_repr_type = std::common_type_t<typename Quantity::repr_type,
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typename Quantity2::repr_type>;
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using r_int_type = std::common_type_t<typename Quantity::ratio_int_type,
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typename Quantity2::ratio_int_type>;
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/* conversion to get y in same units as x: multiply by y/x */
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auto rr = detail::nu_ratio(y.unit(), x.unit());
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if (rr.natural_unit_.is_dimensionless()) {
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r_repr_type r_scale = (static_cast<r_repr_type>(x.scale())
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+ (::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>(y.scale())));
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return Quantity<r_repr_type, r_int_type>(r_scale, x.unit_.template to_repr<r_int_type>());
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} else {
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/* units don't match! */
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return Quantity<r_repr_type, r_int_type>(std::numeric_limits<Repr>::quiet_NaN(),
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x.unit_.template to_repr<r_int_type>());
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}
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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 Quantity<Repr, Int>
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unit_qty(const scaled_unit<Int> & u) {
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return Quantity<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 Repr = double,
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typename Int = std::int64_t>
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inline constexpr Quantity<Repr, Int>
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natural_unit_qty(const natural_unit<Int> & nu) {
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return Quantity<Repr, Int>(1.0, nu);
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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 Quantity2>
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requires quantity2_concept<Quantity> && quantity2_concept<Quantity2>
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constexpr auto
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operator* (const Quantity & x, const Quantity2 & y)
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{
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return Quantity::multiply(x, y);
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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 Quantity2>
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requires quantity2_concept<Quantity> && quantity2_concept<Quantity2>
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constexpr auto
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operator/ (const Quantity & x, const Quantity2 & y)
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{
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return Quantity::divide(x, y);
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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 Quantity2>
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requires quantity2_concept<Quantity> && quantity2_concept<Quantity2>
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constexpr auto
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operator+ (const Quantity & x, const Quantity2 & y)
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{
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return Quantity::add(x, y);
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}
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namespace unit {
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constexpr auto nanogram = natural_unit_qty(nu2::nanogram);
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}
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} /*namespace qty*/
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} /*namespace xo*/
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/** end Quantity.hpp **/
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