scicpp::units::quantity¶

Defined in header <scicpp/core.hpp>

template<typename T, typename Dim, typename Scale, typename Offset = std::ratio<0>> class quantity¶

An arithmetic-like type representing a quantity. The class only stores a value of type T.

It performs compile-time Dimensional analysis to validate Dimensional homogeneity. The quantity dimension Dim is a compile-time constant representing the quantity dimension (for example L^2 T / L). See Implementation notes.

It also provides conversion between units (for example meters to miles), whith conversion factor calculated at compile-time. Scale and Offset are compile-time rational constant representing the affine transform coefficients to convert between units.

Operators¶

Assignment operator: =
Arithmetic operators: ++, --, +=, -=, *=, /=, +, -, *, /
Comparison operators: ==, !=, >=, <=, >, <

Additions, substractions and comparisons can only be performed between quantities of same dimension Dim.

Member functions¶

constexpr T value() const¶

Return the underlying value of the quantity (ex. 1_km.value() returns 1.0). Should mostly be used for printing.

constexpr T eval() const¶

Return the value of a quantity evaluated in the base unit (ex. 1_km.eval() returns 1000.0). Should mostly be used for printing.

Non-member functions¶

template<typename ToQuantity, typename T, typename Dim, typename Scale, typename Offset> constexpr ToQuantity quantity_cast(const quantity<T, Dim, Scale, Offset> &qty)¶

Convert qty to a quantity of type ToQuantity. Used to convert between units when implicit conversion is not allowed, that is if it would result in a loss of precision.

Type traits¶

template<class T> constexpr bool is_quantity_v<T>¶

true if T is a quantity. For example, is_quantity_v<meter<>> == true, but is_quantity_v<double> == false.

template<typename T, typename Dim, typename Scale1, typename Scale2, typename Offset1, typename Offset2> class common_quantity_t¶

Determines the common type of two units.

template<class T> class representation_t¶

Return the representation type if T is a quantity, else simply return T.

For example, representation_t<meter<int>> is int and representation_t<double> is double.

Quantity types arithmetic¶

template<typename Quantity1, typename Quantity2> class quantity_multiply¶

template<typename Quantity1, typename Quantity2> class quantity_divide¶

template<typename Quantity> class quantity_invert¶

template<intmax_t Root, typename Quantity> class quantity_root¶

Use to build derived new quantities from existing ones:

// Energy = Power x Time
template <typename T, typename Scale>
using energy = quantity_multiply<power<T, Scale>, time<T>>;

// Pressure = Force / Area
template <typename T, typename Scale>
using pressure = quantity_divide<force<T, Scale>, area<T>>;

// Frequency = 1 / Time
template <typename T, typename Scale>
using frequency = quantity_invert<time<T, Scale>>;

// Voltage noise density = Electric Potential / sqrt(Bandwidth)
template <typename T, typename Scale>
using voltage_noise_density = quantity_divide<electric_potential<T, Scale>,
                                              quantity_root<2, frequency<T>>>;