macro_rules! system { ( $(#[$quantities_attr:meta])* quantities: $quantities:ident { $($(#[$name_attr:meta])* $name:ident: $unit:ident, $symbol:ident;)+ } $(#[$units_attr:meta])* units: $units:ident { $($module:ident::$quantity:ident,)+ } ) => { ... }; ( $(#[$quantities_attr:meta])* quantities: $quantities:ident { $($(#[$name_attr:meta])* $name:ident: $unit:ident, $symbol:ident;)+ } $(#[$units_attr:meta])* units: $units:ident { $(mod $module:ident::$quantity:ident,)+ } ) => { ... }; ( @quantities $path:path, $V:ty; $($name:ident),+; ($($U:ident),+); $($module:ident::$quantity:ident),+ ) => { ... }; (@replace $_t:tt $sub:ty) => { ... }; }
Expand description
Macro to implement a system of quantities. @...
match
arms are considered private.
$quantities_attr
: System of quantities attributes. Generally used to set documentation comments for the system of quantities.$quantities
: Name of the system of quantities (e.g.ISQ
).$name_attr
: Base quantity attributes. Generally used to set documentation comments for base units.$name
: Name of the base quantities for the system of quantities (e.g.length
,mass
, …). Note that this name must match the module name of the quantity.$unit
: Base unit of the quantity (e.g.meter
,kilogram
).$symbol
: Dimension symbol of the quantity.$units_attr
: System of units attributes. Generally used to set documentation comments for the system of units.$units
: Name of the system of units (e.g.SI
).$module
: Module name of the quantity. When prefixed by themod
keyword the module must already be defined with the#[macro_use]
attribute. A#[macro_use] pub mod $module;
statement is generated if this variable is not prefixed by themod
keyword.$quantity
: Quantity name (e.g.Length
,Mass
, …).
An example invocation is given below for a meter-kilogram-second system. The #[macro_use]
attribute must be used when including the uom
crate to make the system!
macro available.
#[macro_use]
extern crate uom;
system! {
/// System of quantities, Q.
quantities: Q {
length: meter, L;
mass: kilogram, M;
time: second, T;
}
/// System of units, U.
units: U {
mod length::Length,
mod mass::Mass,
mod time::Time,
}
}