The Alicorn.jl package

Dynamically define and manipulate physical units and quantities in Julia

The Alicorn package serves a dual purpose:

  1. Dynamically define and combine physical units based on the International System of Units (SI). This functionality is provided by the Units submodule.
  2. Handle physical quantities and correctly treat their units. This functionality is provided by the Quantities submodule.


This documentation is divided into two parts: The Manual describes how to use Alicorn to define units and handle physical quantities. The Reference documents all types, methods, and constants that form the public API of Alicorn.


  • Alicorn represents units as objects of type AbstractUnit with suitable methods to create and manipulate them
  • Alicorn represents quantities as objects of type AbstractQuantity for scalars and AbstractQuantityArray for vectors and matrices, with suitable methods to create and manipulate them
  • Units can be combined and quantities formed using intuitive arithmetic syntax, no parsing of strings representing units is required
  • New units can be dynamically defined during runtime, no manipulation of source files or configuration files is required
  • Alicorn provides two concrete implementations of AbstractQuantity and AbstractQuantityArray: First, SimpleQuantity and SimpleQuantityArray, which explicitly contain a physical unit and is therefore easy to read and interpret. Second, Quantity and QuantityArray, which store only the physical dimension and reference a common set of InternalUnits. This structure reduces the need for unit conversions and is therefore particularly useful in larger numerical operations.
  • Both kinds of quantities can be freely combined to allow intuitive manipulation of quantities.


The Alicorn.jl package is registered in the General Julia registry and can be installed using Julia's package manager Pkg.jl: In the Julia REPL, add Alicorn to your default Julia environment by running

julia> ]

pkg> add Alicorn

Quick Start

The listing below shows a minimal example of how to use Alicorn. Refer to the Basic Usage section for more details.

First, let us calculate a force as a SimpleQuantity:

julia> using Alicorn

julia> ucat = UnitCatalogue() ;

julia> mass = 2 * (ucat.kilo * ucat.gram)
2 kg

julia> acceleration = 10 * ucat.meter * ucat.second^-2
10 m s^-2

julia> force = mass * acceleration
20 kg m s^-2

julia> inUnitsOf(force, ucat.kilo * ucat.newton)
0.02 kN

We can perform the same caluclation using Quantity, choosing a set of InternalUnits first:

julia> using Alicorn

julia> ucat = UnitCatalogue() ;

julia> intu = InternalUnits(mass = 2 * ucat.gram ) ;

julia> mass = Quantity(2 * (ucat.kilo * ucat.gram), intu)
Quantity{Int64} of dimension M^1 in units of (2 g):

julia> acceleration = Quantity(10 * ucat.meter * ucat.second^-2, intu)
Quantity{Int64} of dimension L^1 T^-2 in units of (1 m, 1 s):

julia> force = mass * acceleration
Quantity{Int64} of dimension M^1 L^1 T^-2 in units of (2 g, 1 m, 1 s):

julia> inUnitsOf(force, ucat.kilo * ucat.newton)
0.02 kN


If you are interested in Alicorn, also have a look at the mature Unitful.jl package. Unitful.jl offers functionalities similar to Alicorn.jl, and more.