Expand description
Units of measurement is a crate that does automatic type-safe zero-cost dimensional analysis. You can create your own systems or use the pre-built International System of Units (SI) which is based on the International System of Quantities (ISQ) and includes numerous quantities (length, mass, time, …) with conversion factors for even more numerous measurement units (meter, kilometer, foot, mile, …). No more crashing your climate orbiter!
§Usage
uom
requires rustc
1.65.0 or later. Add this to your Cargo.toml
:
[dependencies]
uom = "0.36.0"
and this to your crate root:
extern crate uom;
The simple example below shows how to use quantities and units as well as how uom
stops
invalid operations:
extern crate uom;
use uom::si::f32::*;
use uom::si::length::kilometer;
use uom::si::time::second;
fn main() {
let length = Length::new::<kilometer>(5.0);
let time = Time::new::<second>(15.0);
let velocity/*: Velocity*/ = length / time;
let _acceleration = calc_acceleration(velocity, time);
//let error = length + time; // error[E0308]: mismatched types
// Get a quantity value in a specific unit.
let time_in_nano_seconds = time.get::<uom::si::time::nanosecond>();
}
fn calc_acceleration(velocity: Velocity, time: Time) -> Acceleration {
velocity / time
}
See examples provided with the source for more advanced usage including how to create Quantity
type aliases for a different set of base units and how to create an entirely new system of
quantities.
§Features
uom
has multiple Cargo
features for controlling available underlying storage types, the
inclusion of the pre-built International System of Units (SI), support for
Serde, and no_std
functionality. The features are described below. f32
, f64
,
std
, and si
are enabled by default. Features can be cherry-picked by using the
--no-default-features
and --features "..."
flags when compiling uom
or specifying
features in Cargo.toml:
[dependencies]
uom = {
version = "0.36.0",
default-features = false,
features = [
"autoconvert", # automatic base unit conversion.
"usize", "u8", "u16", "u32", "u64", "u128", # Unsigned integer storage types.
"isize", "i8", "i16", "i32", "i64", "i128", # Signed integer storage types.
"bigint", "biguint", # Arbitrary width integer storage types.
"rational", "rational32", "rational64", "bigrational", # Integer ratio storage types.
"complex32", "complex64", # Complex floating point storage types.
"f32", "f64", # Floating point storage types.
"si", "std", # Built-in SI system and std library support.
"serde", # Serde support.
]
}
autoconvert
– Feature to enable automatic conversion between base units in binary operators. Disabling the feature only allows for quantities with the same base units to directly interact. The feature exists to account for compiler limitations where zero-cost code is not generated for non-floating point underlying storage types.usize
,u8
,u16
,u32
,u64
,u128
,isize
,i8
,i16
,i32
,i64
,i128
,bigint
,biguint
,rational
,rational32
,rational64
,bigrational
,complex32
,complex64
,f32
,f64
– Features to enable underlying storage types. At least one of these features must be enabled.f32
andf64
are enabled by default. See the Design section for implications of choosing different underlying storage types.si
– Feature to include the pre-built International System of Units (SI). Enabled by default.std
– Feature to compile with standard library support. Disabling this feature compilesuom
withno_std
. Enabled by default.serde
– Feature to enable support for serialization and deserialization of quantities with the Serde crate. Disabled by default.
§Design
Rather than working with measurement units (meter,
kilometer, foot, mile, …) uom
works with quantities
(length, mass, time, …). This simplifies usage because units are only involved at interface
boundaries: the rest of your code only needs to be concerned about the quantities involved.
This also makes operations on quantities (+, -, *, /, …) have zero runtime cost over using
the raw storage type (e.g. f32
).
uom
normalizes values to the base unit for the
quantity. Alternative base units can be used by executing the macro defined for the system of
quantities (ISQ!
for the SI). uom
supports usize
, u8
, u16
, u32
, u64
, u128
,
isize
, i8
, i16
, i32
, i64
, i128
, bigint
, biguint
, rational
, rational32
,
rational64
, bigrational
, complex32
, complex64
, f32
, and f64
as the underlying
storage type.
A consequence of normalizing values to the base unit is that some values may not be able to be
represented or can’t be precisely represented for floating point and rational underlying
storage types. For example if the base unit of length
is meter
and the underlying storage
type is i32
then values like 1 centimeter
or 1.1 meter
cannot be represented. 1 centimeter
is normalized to 0.01 meter
which can’t be stored in an i32
. uom
only allows
units to be used safely. Users of this library will still need to be aware of implementation
details of the underlying storage type including limits and precision.
§Contributing
Contributions are welcome from everyone. Submit a pull request, an issue, or just add comments
to an existing item. The International Bureau of Weights and Measures is an
international standards organization that publishes the SI Brochure. This document
defines the SI and can be used as a comprehensive reference for changes to uom
. Conversion
factors for non-SI units can be found in NIST Special Publication 811.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as below, without any additional terms or conditions.
§License
Licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
at your option.
Modules§
- Utilities for formatting and printing quantities.
- Primitive traits and types representing basic properties of types.
- International System of Units (SI) and International System of Quantities (ISQ) implementations.
- Unicode string slice manipulation for quantities.
Macros§
- Macro to implement
quantity
type aliases for a specific system of units and value storage type. impl_from
generates generic inter-Kind implementations ofFrom
.- Macro to implement the SI prefixes for multiples of units, submultiples of units and binary multiples of units.
- 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. - Macro to duplicate code on a per-storage type basis. The given code is duplicated in new modules named for each storage type. A type alias,
V
, is generated that code can use for the type.@...
match arms are considered private. - Macro to implement a system of quantities.
@...
match arms are considered private. - Macro to implement a set of measurement units. Note that units manually defined using this macro will not be included in the quantity unit enum or associated functions, or in the
FromStr
implementation. Using this macro will create submodules for the underlying storage types that are enabled (e.g.mod f32
).@...
match arms are considered private.
Enums§
- Operations performed on the constant portion of the conversion factor. Used to help guide optimizations when floating point underlying storage types are used.
Traits§
- Helper trait to identify the zero value of a type at compile time.
- Trait to identify units which have a conversion factor.
- Trait representing a conversion factor.
- Default kind of quantities to allow addition, subtraction, multiplication, division, remainder, negation, and saturating addition/subtraction.