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

The type hierarchy – subtypes and supertypes

In Julia, every value has a type, for example, typeof(2) is Int64 (or Int32 on 32-bit systems). Julia has a lot of built-in types, in fact, a whole hierarchy starting from the type Any at the top. Every type in this structure also has a type, namely, DataType, so it is very consistent. typeof(Any), typeof(Int64), typeof(Complex{Int64}), and typeof(DataType) all return DataType. So, types in Julia are also objects; all concrete types, except tuple types, which are a tuple of the types of its arguments, are of type DataType.


Follow along with the code in type_hierarchy.jl.

This type hierarchy is like a tree; each type has one parent given by the supertype function:

  • supertype(Int64) returns Signed
  • supertype(Signed) returns Integer
  • supertype(Integer) returns Real
  • supertype(Real) returns Number
  • supertype(Number) returns Any
  • supertype(Any) returns Any

A type can have a lot of children or subtypes (a function from the InteractiveUtils package) as follows...