bootstrap.md

Bootstrapping Julia

Installing Julia

Recommended method:

• Download an archive from https://julialang.org/downloads/
• Execute julia or julia.exe as-is
• Link it to your $PATH

Distribution packages usually work well too:

• Debians&Ubuntus: apt install julia
• Iris/Aion: module add lang/Julia

Life in REPL

user@pc $ julia

julia> sqrt(1+1)
1.4142135623730951

julia> println("Well hello there!")
Well hello there!

julia> ?
help?> sqrt

sqrt(x)

Computes the square root .....

REPL modes

Julia interprets some additional keys to make our life easier:

• ?: help mode
• ;: shell mode
• ]: packaging mode (looks like a box!)
• Backspace: quits special mode
• Tab: autocomplete anything
• \... Tab: expand math characters

Managing packages from the package management environment

• Install a package

] add UnicodePlots

• Uninstall a package

] remove UnicodePlots

Loading libraries, modules and packages

• Load a local file (with shared functions etc.)

include("mylibrary.jl")

• Load a package, add its exports to the global namespace

using UnicodePlots

How to write a standalone program?

Your scripts should communicate well with the environment! (that means, among other, you)

#!/usr/bin/env julia

function process_file(filename)

  @info "Processing $filename..."

  # ... do something ...

  if error_detected
    @error "something terrible has happened"
    exit(1)
  end
end

for file in ARGS
    process_file(file)
end

Correct processing of commandline arguments makes your scripts repurposable and configurable.

Workflow: Make a local environment for your script

• Enter a local project with separate package versions

] activate path/to/project

• Install dependencies of the local project

] instantiate

• Execute a script with the project environment

$ julia --project=path/to/project script.jl

(Project data is stored in Project.toml, Manifest.toml.)