concept quantity - kwikius/pqs GitHub Wiki

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Description

A measurable quantity 1 with a unit and a numeric_value 2.

Relation of numeric_value and conversion factor

Notation

type model of notes
Q, Qj, Qk, Qr quantity
U unit
V, Vr dimensionless_quantity
Sm measurement_system
D dimension
Ds simple_dimension
C conversion_factor<...>
value type notes
q Q
qJ Qj
qK Qk
qR Qr local result
vR Vr local result
v V The numeric value of q
b bool

Provides

concept notes
scalar< Q > A model of quantity is implicitly a model of scalar
operation result requires notes
qJ + qK qR DA and provide_operator< Qj, plus, Qk> == true To disable, set impl::provide_operator_plus_impl<Qj,Qk> false
qJ - qK qR DA and provide_operator< Qj ,minus, Qk> == true To disable, set impl::provide_operator_minus_impl<Qj,Qk> false
qJ * qK qR DA and provide_operator< Qj, times, Qk> == true To disable, set impl::provide_operator_times_impl<Qj,Qk> false
qJ * qK vR DA and provide_operator< Qj, times, Qk> == true To disable, set impl::provide_operator_times_impl<Qj,Qk> false
qJ / qK qR DA and provide_operator< Qj, divides, Qk> == true To disable, set impl::provide_operator_divides_impl<Qj,Qk> false
qJ / qK vR DA and provide_operator< Qj, divides, Qk> == true To disable, set impl::provide_operator_divides_impl<Qj,Qk> false
pow<N>(q) qR DA and provide_operator< Qj, pow, std::ratio<N,1> > == true To disable, set impl::provide_operator_pow_impl<Qj,N,1> false
pow<N,D>(q) qR DA and provide_operator< Qj, pow, std::ratio<N,D> > ==true To disable, set impl::provide_operator_pow_impl<Qj,N,D> false
qJ < qK b DA and provide_operator_cmp< Qj, Qk > == true To disable, set impl::provide_operator_cmp_impl<Qj,Qk> false
qJ <= qK b DA and provide_operator_cmp< Qj, Qk > == true To disable, set impl::provide_operator_cmp_impl<Qj,Qk> false
qJ != qK b DA and provide_operator_cmp< Qj, Qk > == true To disable, set impl::provide_operator_cmp_impl<Qj,Qk> false
qJ == qK b DA and provide_operator_cmp< Qj, Qk > == true To disable, set impl::provide_operator_cmp_impl<Qj,Qk> false
qJ >= qK b DA and provide_operator_cmp< Qj, Qk > == true To disable, set impl::provide_operator_cmp_impl<Qj,Qk> false
qJ > qK b DA and provide_operator_cmp< Qj, Qk > == true To disable, set impl::provide_operator_cmp_impl<Qj,Qk> false
alias_template result notes
get_measurement_system< Q > Sm The measurement_system of U
get_dimension< Q > D the dimension of U
get_conversion_factor< Q > C the conversion factor for U
get_simple_dimension< Q > Ds the simple_dimension of U
get_unit< Q > U
get_numeric_type< Q > V
inline_bool_constant value notes
dimensionally_equivalent< Qj, Qk > true if Qj and Qk are dimensionally
equivalent else false		 applies std::remove_cvref_t
to Qj,Qk before testing
same_measurement_system< Qj, Qk > true if units of Qj and Qk are
in same measurement system
else false		 applies std::remove_cvref_t
to Qj,Qk before testing

Requires:

inline_bool_constant value notes
impl::is_quantity_impl< Q > true states that Q
fulfills the requirements below
typestruct result notes
impl::get_unit_impl< Q > U
impl::get_numeric_type_impl< Q > V
function result notes
get_numeric_value( q ) v

Relation of numeric value of quantities of same dimension:

For a model of quantity q, the conversion_factor is the factor by which to multiply the numeric_value of q, to convert q to a dimensionally_equivalent quantity in the same measurement system, with a conversion_factor that evaluates to 1.
Let Qb be a model of quantity where evaluate<get_conversion_factor< Qb > >() == 1.
Let Q be a dimensionally_equivalent model of quantity in same measurement_system as Qb , where evaluate<get_conversion_factor<Q> >() != 1.

   using namespace pqs;

   using Qb = si::length::m<>;
   using Q  = si::length::ft<>;

   static_assert( same_measurement_system< Q,Qb > );
   static_assert( evaluate<get_conversion_factor< Qb > >() == 1 );
   static_assert( evaluate<get_conversion_factor< Q > >() != 1 );

   constexpr dimensionless_quantity n = -12345.678;
   
   constexpr Q  q{n};
   constexpr Qb qB = q;

   static_assert( 
      get_numeric_value(qB) == 
         get_numeric_value(q) * evaluate<get_conversion_factor<Q> >() 
   );

Notes

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