Julia Lab Examples

Twenty-one single-file programs, each short enough to read in a minute and complete enough to run. They follow the lesson order of the track: foundations first, then functions and scope, collections and types, and finally exceptions and files. Open a file, run it with julia file.jl, then change one thing and run it again — that second run is where the learning happens.

Every example is self-contained: no package to install, no project to activate, nothing but the standard library. Where a lesson introduced a concept — implicit types, multiple dispatch, the type tree, lexical scope — there is a program here that shows it working, and one line you can break to see what happens when it is wrong.

Foundations

Variables, expressions, and the ways Julia decides what to do next. Start here: these files introduce the values (Int, Float64, Bool, String, Char) that every later example uses.

#	Description	Link
1	Variables and implicit types	View
2	Literals and operators	View
3	Boolean values and logic	View
4	Single-branch conditional	View
5	Comparison and branching on input	View
6	Character input with an if/elseif ladder	View
7	Conditional loop with `while`	View
8	Counting loop with `continue`	View
9	Nested iteration over two ranges	View

Functions & Scope

A function is the unit of reuse and the unit of method dispatch. These four programs show declaration, a declared return type, and the difference between global, local, and let-block scope — the rule that explains most "why is my variable nothing?" questions.

#	Description	Link
10	Declaring and calling a function	View
11	A function with a declared return type	View
12	Global versus local variables	View
13	Nested `let` blocks	View

Collections & Types

Arrays, tuples, dictionaries, and the type machinery underneath them: abstract and primitive types, composite structs, and parametric types. Run these with the REPL open and inspect typeof(x) after each line.

#	Description	Link
14	Arrays: one and two dimensional	View
15	Tuples: indexing and destructuring	View
16	Dictionaries: keys to values	View
17	The type tree: abstract and primitive types	View
18	Composite types with `mutable struct`	View
19	Parametric types: `Point{T}`	View

Errors & Files

Two programs about failure: how to guarantee a file is closed when something throws, and how to catch an error and return a useful value instead of crashing. Delete the try in either one and watch the behaviour change.

#	Description	Link
20	Opening and closing a file with `try/finally`	View
21	Recovering from an error with `try/catch`	View

How to use these examples. Run each file straight from the track's demo folder — julia roadmap/julia/demo/01_variables.jl — or open it in the code viewer and copy it out. Files 5 and 6 read from standard input, so they expect you to type a character and press Enter. Nothing here needs a package, which makes this folder a good place to practise without touching a project environment.

Larger, multi-file programs follow in Study Projects.