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

Reflection capabilities

We saw in this chapter that code in Julia is represented by expressions that are data structures of the Expr type. The structure of a program and its types can therefore be explored programmatically just like any other data. This means that a running program can dynamically discover its own properties, which is called reflection. We have already encountered some of these macros or functions before:

  • Use the @isdefined macro to check whether a variable is already declared, for example if a is not declared, you get:
@isdefined a #> false
  • Use the typeof and InteractiveUtils.subtypes to query the type hierarchy (refer to Chapter 6, More on Types, Methods, and Modules)
  • Use the methods(f) to see all the methods of a function f (refer to Chapter 3, Functions)
  • names and types: given a type Person:
mutable struct Person 
    name:: String 

Then, fieldnames(Person) returns the field names as a tuple of symbols: (:name, :height)

Person.types returns a tuple...