Book Image

Julia 1.0 Programming - Second Edition

By : Ivo Balbaert
Book Image

Julia 1.0 Programming - Second Edition

By: Ivo Balbaert

Overview of this book

The release of Julia 1.0 is now ready to change the technical world by combining the high productivity and ease of use of Python and R with the lightning-fast speed of C++. Julia 1.0 programming gives you a head start in tackling your numerical and data problems. You will begin by learning how to set up a running Julia platform, before exploring its various built-in types. With the help of practical examples, this book walks you through two important collection types: arrays and matrices. In addition to this, you will be taken through how type conversions and promotions work. In the course of the book, you will be introduced to the homo-iconicity and metaprogramming concepts in Julia. You will understand how Julia provides different ways to interact with an operating system, as well as other languages, and then you'll discover what macros are. Once you have grasped the basics, you’ll study what makes Julia suitable for numerical and scientific computing, and learn about the features provided by Julia. By the end of this book, you will also have learned how to run external programs. This book covers all you need to know about Julia in order to leverage its high speed and efficiency for your applications.
Table of Contents (17 chapters)
Title Page
Copyright and Credits
Packt Upsell

User-defined and composite types

In Julia, as a developer you can define your own types to structure data used in applications. For example, if you need to represent points in a three-dimensional space, you can define a type Point, as follows:

# see the code in Chapter 6\user_defined.jl: 
mutable struct Point 

mutable here means that Point values can be modified. If your type values cannot be changed, simply use struct.

The type Point is a concrete type. Objects of this type can be created as p1 = Point(2, 4, 1.3), and it has no subtypes: typeof(p1) returns Point (constructor with 2 methods), subtypes(Point)returns 0-element Array{Any,1}.


Such a user-defined type is composed of a set of named fields with an optional type annotation; that's why it is a composite type, and its type is also DataType. If the type of a named field is not given, then it is Any. A composite type is similar to struct in C, or a class without methods in Java.