Julia

Installation

Juno

Juno is an IDE for Julia. It consists of a set of packages added to Atom. Most items can be accessed from the Atom control palette Ctrl + Shift + P
Shortcuts:

• Ctrl + Enter Evaluate current selection
• Shift + Enter Evaluate current section and jump to next.

Basic Usage

Package Management

Guide Initializing a new project

cd project_folder
julia
] activate ./
# Add your packages

Loading an existing project

cd project_folder
julia
using Pkg;
Pkg.activate("./");
Pkg.instantiate();

String Interpolation

"Variable x is $x, y is $y, and x+y is $(x+y)"

Arrays

Main article: https://en.wikibooks.org/wiki/Introducing_Julia/Arrays_and_tuples

// Make an 1d array of Float64.
// Equivalent to [0.0, 0.0, 0.0]
myArr = zeros(4);

// Make a 1d array of Float64 left to uninitialized values
myArr = Array{Float64,1}(undef, 3)

// Convert an iterable to an array with collect
myArr = collect(1:3)

// Reference copy
a = [1, 2, 3];
b = [4, 5, 6];
b = a

// Shallow copy
a = [1, 2, 3];
b = [4, 5, 6];
// elementwise equals operator
b .= a
// or b[:] = a
// or b = copy(a) (this will discard the original b)

// Basic functionality
// Call functions elementwise by adding . after the function name
a = [1, 5, 99];
a = clamp.(a, 1, 11);
// a is now [1, 5, 11]
// Equivalent to clamp!(a, 1, 11)

// Julia also has map, foldl, foldr, reduce

Higher order functions

Julia supports high-order functions.

ts = ((a, b) -> (c, d) -> a + b + c + d)(1,2);

The call with arguments (1,2) returns a function.
Then ts is equivalent to

ts = (c, d) -> 1 + 2 + c + d;

You can also use the full function(a,b) syntax.

Animation Loop

You can use Timer(callback, delay, interval). This is similar to SetInterval in JavaScript.
End the loop with close(animate).

animate = Timer(function(t)
    println("Animating")
end, 0; interval=1/60)

Graphics

Main article: Graphics in Julia

You can use MeshCat.jl to create visualizations to view in a web browser.
These visualizations are powered by WebGL using three.js.
Note that MeshCat.jl only exposes a small subset of three.js's features so I would not recommend it for creating highly intricate or interactive experiences at the moment.
MeshCat.jl is built using WebIO.jl.

Useful Packages

MeshCat.jl

Link
A wrapper for graphics visualizations around three.js. This opens in a web browser but can be used for making helium apps. See Graphics in Julia for more details on how to use this.