specfem::units::Quantity

Dim

template<int M, int L, int T, int A = 0>
struct Dim

Compile-time physical dimension representation.

Encodes dimensional exponents for mass, length, time, and angle. The angle dimension distinguishes frequency types (Hertz vs Omega).

Template Parameters:

  • M – Mass exponent

  • L – Length exponent

  • T – Time exponent

  • A – Angle exponent (0 for Hertz, 1 for rad/s)

Public Static Attributes

static constexpr int mass = M

Mass dimension exponent.

static constexpr int length = L

Length dimension exponent.

static constexpr int time = T

Time dimension exponent.

static constexpr int angle = A

Angle dimension exponent.

Quantity

template<typename D, typename Scale = std::ratio<1, 1>>
class Quantity

Type-safe physical quantity with compile-time dimensional analysis.

Represents a physical quantity with dimensions D and scale factor Scale. Prevents unit mismatches at compile time through template parameters. Arithmetic operations preserve dimensional correctness.

Meters distance(100.0);
Seconds time(10.0);
Velocity speed = distance / time;  // Returns Velocity(10.0)

Template Parameters:

  • D – Dimension type (Dim<M,L,T,A>)

  • Scale – Unit scale as std::ratio (default: 1/1 for SI base units)

Public Functions

inline explicit constexpr Quantity(type_real v = 0.0) noexcept

Construct a quantity from a raw value.

Parameters:

v – Value in the specified units (default: 0.0)

inline constexpr type_real raw() const noexcept

Extract the raw numeric value.

Explicit method to emphasize stripping units is intentional.

Returns:

constexpr type_real Numeric value without units

inline explicit constexpr operator type_real() const noexcept

Explicit conversion to raw numeric value.

Returns:

constexpr type_real Numeric value without units

inline constexpr Quantity operator-() const noexcept

Unary negation.

ratio_value

template<typename R>
constexpr type_real specfem::units::ratio_value = static_cast<type_real>(R::num) / static_cast<type_real>(R::den)

Compile-time conversion of std::ratio to a scalar value.

Template Parameters:

R – std::ratio type

Return:

constexpr type_real Ratio as a floating-point value

specfem::units::SI Dimensions

Warning

doxygennamespace: Cannot find namespace “specfem::units::SI” in doxygen xml output for project “specfem++” from directory: _build/doxygen/xml

Named Quantities

Warning

doxygentypedef: Cannot find typedef “specfem::units::Dimensionless” in doxygen xml output for project “specfem++” from directory: _build/doxygen/xml

using specfem::units::Grams = Quantity<SI::DimMass>

Mass in grams.

using specfem::units::Kilograms = Quantity<SI::DimMass, std::ratio<1000, 1>>

Mass in kilograms.

using specfem::units::Seconds = Quantity<SI::DimTime>

Time in seconds.

using specfem::units::Meters = Quantity<SI::DimLength>

Length in meters.

using specfem::units::Kilometers = Quantity<SI::DimLength, std::ratio<1000, 1>>

Length in kilometers.

using specfem::units::Radians = Quantity<SI::DimAngle>

Angle in radians.

using specfem::units::GramPerCubicMeter = Quantity<SI::DimDensity>

Density ( \( \mathrm{g/m^3} \))

using specfem::units::KilogramPerCubicMeter = Quantity<SI::DimDensity, std::ratio<1000, 1>>

Density ( \( < \mathrm{kg/m^3} \))

using specfem::units::MetersPerSecond = Quantity<SI::DimVelocity>

Velocity (m/s)

using specfem::units::KilometersPerSecond = Quantity<SI::DimVelocity, std::ratio<1000, 1>>

Velocity (km/s)

using specfem::units::Hertz = Quantity<SI::DimFrequency>

Frequency in Hertz (cycles/s)

using specfem::units::Omega = Quantity<SI::DimAngularFrequency>

Angular frequency (rad/s)

using specfem::units::Pascal = Quantity<SI::DimPressure>

Pressure (Pa)

using specfem::units::Megapascal = Quantity<SI::DimPressure, std::ratio<1000000, 1>>

Pressure (MPa)