Installing Development Tools

Julia REPL

A REPL, or read-eval-print loop, represents a language "shell" or program that allows the user to communicate with the programming language interactively with immediate feedback. This allows for exploring the language more deeply than via a script, with rapid prototyping being much quicker and easier to perform.

The Julia REPL is included by default in every Julia installation and boasts a number of features to the point that it alone can almost be considered a proper IDE. It should appear the moment you enter julia into your terminal:

   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.9.2 (2023-07-05)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> 

We won't go into every feature that the REPL provides, however here is a quick list that most Julia users should know to make the most of this shell:

• There are 5 Julia REPL modes that serve separate purposes:

  1. The Julian (default) mode wherein one can write, load, and test out code
  2. Help mode for printing documentation for functions, keywords, etc.
  3. Pkg mode for working with the included package manager and manipulating dependencies/packages
  4. Shell mode to execute system commands (run a terminal from Julia which itself is running from a terminal!)
  5. Search modes (forward, reverse) to look through your history of inputs

• If you have a code editor installed on your development machine, you can go back and forth between the Julia session and the editor by entering julia> edit("<name of file>"). You can jump right back into the Julia session once you're finished!
• You can get a list of matches to a partially written word by entering the TAB key, which also serves to render an Unicode symbol in the REPL (full list available in the Unicode Input section of the Julia manual):

  julia> pri[TAB]
  primitive type  print           println         printstyled
  julia> \pi[TAB] # renders π

• You can run a standalone script by entering include("<name of script>") in Julian mode. For greater control, the equivalent of Python3's if __name__ == __main__ condition would be if abspath(<name of program file>) == @__FILE__

julia> struct Point
        x::Int
        y::Int
    end

julia> struct Point
        x::Int
        z::Int
    end
ERROR: invalid redefinition of constant Point
Stacktrace:
[1] top-level scope
@ REPL[2]:1

To learn more, see the The Julia REPL section in the Julia manual.

Visual Studio Code extension

The Julia organization officially maintains the Julia vscode extension, which provides a complete IDE solution for developing in Julia. This boasts a number of advantages compared to a REPL solution:

• Built-in syntax highlighting and code completion
• GUI interaction for managing options and commands
• Advanced profiling/debugging features
• Additional extensions support

To install vscode, follow the instructions on how to install the official binary for your development machine from the official website. Next, click on the Extension icon in the side Activity Bar and search for "Julia". The official Julia extension should be the first extension available. You can also install Julia within the Quick Open input panel by pressing Ctrl + P and entering ext install julialang.language-julia.

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Install the extension and restart vscode. We also recommend installing some additional extensions that will further improve the development experience:

• Even Better TOML (ext install tamasfe.even-better-toml) for working with the package TOML files (Project.toml, Manifest.toml, Artifacts.toml,...)
• GitLens (ext install eamodio.gitlens) for enhancing Git workflows

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You can experiment with Julia extension features in the Quick Open panel by writing Julia and consulting the available options. To learn more, visit the Julia in Visual Studio Code page in the official vscode docs. You can also visit the Julia extension website to learn more about what features are available.