[−][src]Macro uom::quantity
Macro to implement a quantity and associated measurement units. Note
that this macro must be executed in direct submodules of the module where the
system!
macro was executed. @...
match arms are considered private.
$quantity_attr
: Quantity attributes. Generally used to set documentation comments for the quantity.$quantity
: Quantity name (e.g.Length
).$description
: Quantity description (e.g."length"
).$dim_attr
: Dimension attributes. Generally used to set documentation comments for the quantity's dimension type alias.$system
: System of quantities type (e.g.ISQ
).$dimension
: Power of a factor for each base quantity in the system. Power should be represented as atypenum
type-level integer (e.g.N1
,Z0
,P1
,P2
, ...).$kind
: Kind of the quantity. Optional. This variable should only be specified when defining a quantity that has the same dimensions as another quantity but isn't comparable. When not specifieduom::Kind
is used.$unit
: Unit name (e.g.meter
,foot
).$conversion
: Conversion (coefficient and constant factor) from the unit to the base unit of the quantity (e.g.3.048_E-1
to convertfoot
tometer
.1.0_E0, 273.15_E0
to convertcelsius
tokelvin
.). The coefficient is required and the constant factor is optional. Note that using a unit with a non-zero constant factor is not currently supported as a base unit.$abbreviation
: Unit abbreviation (e.g."m"
).$singular
: Singular unit description (e.g."meter"
).$plural
: Plural unit description (e.g."meters"
).
An example invocation is given below for the quantity of length in a meter-kilogram-second
system. The #[macro_use]
attribute must be used when including the uom
crate to make the
quantity!
macro available.
#[macro_use] extern crate uom; #[macro_use] mod length { quantity! { /// Length (base unit meter, m<sup>1</sup>). quantity: Length; "length"; /// Length dimension, m<sup>1</sup>. dimension: Q<P1 /*length*/, Z0 /*mass*/, Z0 /*time*/>; units { @meter: 1.0E0; "m", "meter", "meters"; @foot: 3.048E-1; "ft", "foot", "feet"; } } }