Roland Conybeare
d1fa15f248
git-subtree-dir: xo-unit git-subtree-mainline:e9ee6992cagit-subtree-split:b531e382c2
562 lines
24 KiB
C++
562 lines
24 KiB
C++
/** @file xquantity.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 "quantity_ops.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 xquantity
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* @brief represent a scalar quantity with polymorphic units.
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*
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* - @p Repr type used represent a dimensionless multiple of a natural unit.
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*
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* Constexpr implementation, but units are explicitly represented:
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* @code
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* sizeof(xquantity) > sizeof(xquantity::repr_type)
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* @endcode
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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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* See for example <a href="https://github.com/rconybea/xo-pyutil">xo-pyutil</a>
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*
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* See @ref quantity for implementation with units established at compile time
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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 xquantity {
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public:
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/** @defgroup xquantity-type-traits xquantity type traits **/
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///@{
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/** @brief runtime representation for this value's scale **/
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using repr_type = Repr;
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/** @brief runtime representation for this value's unit **/
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using unit_type = natural_unit<Int>;
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/** @brief type used for numerator and denominator in basis-unit scalefactor ratios **/
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using ratio_int_type = Int;
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/** @brief double-width type for numerator and denominator of intermediate
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* scalefactor ratios. Use to mitigate loss of precision during computation
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* of conversion factors between units with widely-differing magnitude
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**/
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using ratio_int2x_type = detail::width2x_t<typename unit_type::ratio_int_type>;
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///@}
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public:
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/** @defgroup xquantity-ctors xquantity constructors **/
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///@{
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/** create dimensionless, zero quantity **/
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constexpr xquantity()
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: scale_{0}, unit_{natural_unit<Int>()} {}
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/** create quantity representing multiple of @p scale times @p unit **/
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constexpr xquantity(Repr scale,
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const natural_unit<Int> & unit)
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: scale_{scale}, unit_{unit} {}
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/** create quantity representing multiple of @p scale times @p unit.
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*
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* Collects outer scalefactors (if any) from @p unit,
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* so for example:
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*
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* @code
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* using namespace xo::qty;
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* xquantity q(123, u::meter * u::millimeter);
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*
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* q.scale() --> 0.123
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* @endcode
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**/
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constexpr xquantity(Repr scale,
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const scaled_unit<Int> & unit)
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:
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scale_(scale
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* unit.outer_scale_factor_.template convert_to<double>()
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* ((unit.outer_scale_sq_ == 1.0)
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? 1.0
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: ::sqrt(unit.outer_scale_sq_))
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),
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unit_{unit.natural_unit_} {}
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///@}
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/** @defgroup xquantity-constants static xquantity constants **/
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///@{
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/** false since unit information may be unknown at compile time.
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* Coordinates with @c quantity::always_constexpr_unit
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**/
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static constexpr bool always_constexpr_unit = false;
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///@}
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/** @defgroup xquantity-access-methods xquantity access methods **/
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///@{
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/** get member @ref scale_ **/
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constexpr const repr_type & scale() const { return scale_; }
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/** get member @ref unit_ **/
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constexpr const unit_type & unit() const { return unit_; }
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/** true iff this quantity has no dimension **/
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constexpr bool is_dimensionless() const { return unit_.is_dimensionless(); }
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/** return abbreviation for quantities with this unit **/
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constexpr nu_abbrev_type abbrev() const { return unit_.abbrev(); }
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///@}
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/** @defgroup xquantity-arithmetic-support**/
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///@{
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/** create unit quantity with same unit as @c this **/
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constexpr xquantity unit_qty() const { return xquantity(1, unit_); }
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/** create zero quantity with same unit as @c this **/
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constexpr xquantity zero_qty() const { return xquantity(0, unit_); }
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/** create quantity representing reciprocal of @c this **/
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constexpr xquantity reciprocal() const { return xquantity(1.0 / scale_, unit_.reciprocal()); }
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/** create quantity representing this value scaled by dimensionless mutliplier @p x **/
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template <typename Dimensionless>
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requires std::is_arithmetic_v<Dimensionless>
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constexpr auto scale_by(Dimensionless x) const {
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return xquantity(x * this->scale_, this->unit_);
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}
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/** create quantity representing this value scaled by dimensionless multiplier @p 1/x **/
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template <typename Dimensionless>
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requires std::is_arithmetic_v<Dimensionless>
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constexpr auto divide_by(Dimensionless x) const {
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return xquantity(this->scale_ / x, this->unit_);
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}
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/** create quantity representing dimensionless numerator @p x divided by this value **/
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template <typename Dimensionless>
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requires std::is_arithmetic_v<Dimensionless>
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constexpr auto divide_into(Dimensionless x) const {
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return xquantity(x / this->scale_, this->unit_.reciprocal());
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}
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/** multiply two @c xquantity values, or a mixed (@c xquantity, @c quantity) pair **/
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template <typename Quantity2>
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static constexpr
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auto multiply(const xquantity & x, const Quantity2 & y) {
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using r_repr_type = std::common_type_t<typename xquantity::repr_type,
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typename Quantity2::repr_type>;
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using r_int_type = std::common_type_t<typename xquantity::ratio_int_type,
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typename Quantity2::ratio_int_type>;
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using r_int2x_type = std::common_type_t<typename xquantity::ratio_int2x_type,
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typename Quantity2::ratio_int2x_type>;
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auto rr = detail::su_product<r_int_type, r_int2x_type>(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_factor_.template convert_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 xquantity<r_repr_type, r_int_type>(r_scale,
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rr.natural_unit_);
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}
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/** compute quotient @p x / @p y, where @p x and @p y are xquantities **/
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template <typename Quantity2>
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static constexpr
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auto divide(const xquantity & x, const Quantity2 & y) {
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using r_repr_type = std::common_type_t<typename xquantity::repr_type,
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typename Quantity2::repr_type>;
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using r_int_type = std::common_type_t<typename xquantity::ratio_int_type,
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typename Quantity2::ratio_int_type>;
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using r_int2x_type = std::common_type_t<typename xquantity::ratio_int2x_type,
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typename Quantity2::ratio_int2x_type>;
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auto rr = detail::su_ratio<r_int_type, r_int2x_type>(x.unit(), y.unit());
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/* note: su_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_factor_.template convert_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 xquantity<r_repr_type, r_int_type>(r_scale,
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rr.natural_unit_);
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}
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/** compute sum @p x + @p y, where @p x and @p y are xquantities **/
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template <typename Quantity2>
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static constexpr
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auto add(const xquantity & x, const Quantity2 & y) {
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using r_repr_type = std::common_type_t<typename xquantity::repr_type,
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typename Quantity2::repr_type>;
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using r_int_type = std::common_type_t<typename xquantity::ratio_int_type,
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typename Quantity2::ratio_int_type>;
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using r_int2x_type = std::common_type_t<typename xquantity::ratio_int2x_type,
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typename Quantity2::ratio_int2x_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::su_ratio<r_int_type, r_int2x_type>(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_factor_.template convert_to<r_repr_type>()
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* static_cast<r_repr_type>(y.scale())));
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return xquantity<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 xquantity<r_repr_type, r_int_type>(std::numeric_limits<r_repr_type>::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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/** compute difference @p x - @p y, where @p x and @p y are xquantities **/
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template <typename Quantity2>
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static constexpr
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auto subtract(const xquantity & x, const Quantity2 & y) {
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using r_repr_type = std::common_type_t<typename xquantity::repr_type,
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typename Quantity2::repr_type>;
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using r_int_type = std::common_type_t<typename xquantity::ratio_int_type,
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typename Quantity2::ratio_int_type>;
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using r_int2x_type = std::common_type_t<typename xquantity::ratio_int2x_type,
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typename Quantity2::ratio_int2x_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::su_ratio<r_int_type, r_int2x_type>(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_factor_.template convert_to<r_repr_type>()
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* static_cast<r_repr_type>(y.scale())));
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return xquantity<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 xquantity<r_repr_type, r_int_type>(std::numeric_limits<r_repr_type>::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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///@}
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/** @defgroup xquantity-unit-conversion **/
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///@{
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/** create quantity representing the same value, but in units of @p unit2 **/
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constexpr
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auto rescale(const natural_unit<Int> & unit2) const {
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/* conversion factor from .unit -> unit2*/
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auto rr = detail::su_ratio<ratio_int_type,
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ratio_int2x_type>(this->unit_, unit2);
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if (rr.natural_unit_.is_dimensionless()) {
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repr_type r_scale = (::sqrt(rr.outer_scale_sq_)
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* rr.outer_scale_factor_.template convert_to<repr_type>()
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* this->scale_);
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return xquantity(r_scale, unit2);
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} else {
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return xquantity(std::numeric_limits<repr_type>::quiet_NaN(), unit2);
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}
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}
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constexpr
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auto rescale_ext(const scaled_unit<Int> & unit2) const {
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/* conversion factor from .unit -> unit2*/
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auto rr = detail::su_ratio<ratio_int_type,
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ratio_int2x_type>(unit_,
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unit2.natural_unit_);
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if (rr.natural_unit_.is_dimensionless()) {
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/* NOTE: test for unit .outer_scale_sq values to get constexpr result with c++23
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* and integer dimension powers.
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*
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* NOTE: we don't intend to support mixed-unit quantities.
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* If we change intention, will need to take into account
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* (s_scaled_unit.outer_scale_factor_, s_scaled_unit.outer_scale_sq_)
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*/
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repr_type r_scale
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= ((((rr.outer_scale_sq_ == 1.0)
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&& (unit2.outer_scale_sq_ == 1.0))
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? 1.0
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: ::sqrt(rr.outer_scale_sq_ / unit2.outer_scale_sq_))
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* rr.outer_scale_factor_.template convert_to<repr_type>()
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* this->scale_
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/ unit2.outer_scale_factor_.template convert_to<repr_type>());
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return xquantity(r_scale, unit2);
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} else {
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return xquantity(std::numeric_limits<repr_type>::quiet_NaN(), unit2);
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}
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}
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///@}
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/** @defgroup xquantity-comparison-support xquantity comparison support methods **/
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///@{
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/** perform 3-way comparison between @c xquantity values @p x and @p y **/
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template <typename Quantity2>
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static constexpr
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auto compare(const xquantity & x, const Quantity2 & y) {
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xquantity y2 = y.rescale(x.unit_);
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return x.scale() <=> y2.scale();
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}
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///@}
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/** @defgroup xquantity-operators xquantity operators **/
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///@{
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/** add @p x in-place, converting units if necessary **/
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template <typename Quantity2>
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xquantity & operator+= (const Quantity2 & x) {
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*this = *this + x;
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return *this;
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}
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/** unary negation; preserves unit information **/
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xquantity operator-() const {
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return xquantity(-scale_, unit_);
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}
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/** subtract @p x in-place, converting units if necessary **/
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template <typename Quantity2>
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xquantity & operator-= (const Quantity2 & x) {
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*this = *this - x;
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return *this;
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}
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/** multiply @p x in-place, converting units if necessary
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*
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* @note: unlike @c quantity::operator*=, may change dimension of lhs
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**/
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template <typename Quantity2>
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xquantity & operator*= (const Quantity2 & x) {
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*this = *this * x;
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return *this;
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}
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/** divide @p x in-place, converting units if necessary
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*
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* @note: unlike @c quantity::operator/=, may change dimension of lhs
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**/
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template <typename Quantity2>
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xquantity & operator/= (const Quantity2 & x) {
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*this = *this / x;
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return *this;
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}
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///@}
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private:
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/** @defgroup xquantity-instance-vars **/
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///@{
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/** quantity represents this multiple of a unit amount **/
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Repr scale_ = Repr{};
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/** unit for this quantity **/
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natural_unit<Int> unit_;
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///@}
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}; /*xquantity*/
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/** note: won't have constexpr result until c++26 (when @c sqrt(), @c 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 xquantity<Repr, Int>
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unit_qty(const scaled_unit<Int> & u)
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{
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return xquantity<Repr, Int>
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(u.outer_scale_factor_.template convert_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 @c sqrt(), @c 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 xquantity<Repr, Int>
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natural_unit_qty(const natural_unit<Int> & nu) {
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return xquantity<Repr, Int>(1.0, nu);
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}
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/** note: won't have constexpr result until c++26 (when @c sqrt(), @c pow() are constexpr)
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**/
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template <typename Q1, typename Q2>
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requires (quantity_concept<Q1>
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&& quantity_concept<Q2>
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&& (!Q1::always_constexpr_unit || !Q2::always_constexpr_unit))
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constexpr auto
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operator* (const Q1 & x, const Q2 & y)
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{
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return Q1::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>
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requires quantity_concept<Quantity>
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constexpr auto
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operator* (double x, const Quantity & y)
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{
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return y.scale_by(x);
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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>
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requires quantity_concept<Quantity>
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constexpr auto
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operator* (const Quantity & x, double y)
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{
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return x.scale_by(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 quantity_concept<Quantity> && quantity_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: doesn not require unit scaling, so constexpr with c++23 **/
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template <typename Quantity, typename Dimensionless>
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requires quantity_concept<Quantity> && std::is_arithmetic_v<Dimensionless>
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constexpr auto
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operator/ (const Quantity & x, Dimensionless y)
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{
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return x.divide_by(y);
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}
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/** note: doesn not require unit scaling, so constexpr with c++23 **/
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template <typename Dimensionless, typename Quantity>
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requires std::is_arithmetic_v<Dimensionless> && quantity_concept<Quantity>
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constexpr auto
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operator/ (Dimensionless x, const Quantity & y)
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{
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return y.divide_into(x);
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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 quantity_concept<Quantity> && quantity_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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/** 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>
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requires quantity_concept<Quantity>
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constexpr auto
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operator+ (const Quantity & x, double y)
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{
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return x + Quantity(y, u::dimensionless);
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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>
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requires quantity_concept<Quantity>
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constexpr auto
|
|
operator+ (double x, const Quantity & y)
|
|
{
|
|
return Quantity(x, u::dimensionless) + y;
|
|
}
|
|
|
|
/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
|
|
**/
|
|
template <typename Quantity, typename Quantity2>
|
|
requires (quantity_concept<Quantity>
|
|
&& quantity_concept<Quantity2>)
|
|
constexpr auto
|
|
operator- (const Quantity & x, const Quantity2 & y)
|
|
{
|
|
return Quantity::subtract(x, y);
|
|
}
|
|
|
|
/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
|
|
**/
|
|
template <typename Quantity>
|
|
requires quantity_concept<Quantity>
|
|
constexpr auto
|
|
operator- (const Quantity & x, double y)
|
|
{
|
|
return x - Quantity(y, u::dimensionless);
|
|
}
|
|
|
|
/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
|
|
**/
|
|
template <typename Quantity>
|
|
requires quantity_concept<Quantity>
|
|
constexpr auto
|
|
operator- (double x, const Quantity & y)
|
|
{
|
|
return Quantity(x, u::dimensionless) - y;
|
|
}
|
|
|
|
/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
|
|
**/
|
|
template <typename Quantity>
|
|
requires quantity_concept<Quantity>
|
|
constexpr auto
|
|
operator== (const Quantity & x, double y)
|
|
{
|
|
return (x == Quantity(y, u::dimensionless));
|
|
}
|
|
|
|
/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
|
|
**/
|
|
template <typename Quantity>
|
|
requires quantity_concept<Quantity>
|
|
constexpr auto
|
|
operator== (double x, const Quantity & y)
|
|
{
|
|
return (Quantity(x, u::dimensionless) == y);
|
|
}
|
|
|
|
/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
|
|
**/
|
|
template <typename Quantity, double>
|
|
requires quantity_concept<Quantity>
|
|
constexpr auto
|
|
operator<=> (const Quantity & x, double y)
|
|
{
|
|
return Quantity::compare(x, Quantity(y, u::dimensionless));
|
|
}
|
|
|
|
/** note: won't have constexpr result until c++26 (when ::sqrt(), ::pow() are constexpr)
|
|
**/
|
|
template <typename Quantity, double>
|
|
requires quantity_concept<Quantity>
|
|
constexpr auto
|
|
operator<=> (double x, const Quantity & y)
|
|
{
|
|
return Quantity::compare(Quantity(x, u::dimensionless), y);
|
|
}
|
|
|
|
namespace xu {
|
|
constexpr auto nanogram = xquantity(1.0, u::nanogram);
|
|
}
|
|
} /*namespace qty*/
|
|
} /*namespace xo*/
|
|
|
|
/** end xquantity.hpp **/
|