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
Contributors
Preface
Index

Optional and keyword arguments


When defining functions, one or more arguments can be given a default value such asf(arg = val). If no parameter is supplied for arg, then val is taken as the value of arg. The position of these arguments in the function's input is important, just as it is for normal arguments; that's why they are called optional positional arguments. Here is an example of anf function with an optional argument b:

# code in arguments.jl: 
f(a, b = 5) = a + b

 

 

For example, if it's f(1), then it returns 6; f(2, 5) returns 7; and f(3) returns 8. However, calling it with f() or f(1,2,3) returns an error, because there is no matching function f with zero or three arguments. These arguments are still only defined by position: calling f(2, b = 5) raises an error as ERROR: function f does not accept keyword arguments.

Until now, arguments were only defined by position. For code clarity, it can be useful to explicitly call the by name, so they are called optional keyword arguments. Because...