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

Defining macros


In previous chapters, we have already used macros, such as @printf, in Chapter 2, Variables, Types, and Operations, and @time in Chapter 3, Functions. Macros are like functions, but instead of values they take expressions (which can also be symbols or literals) as input arguments. When a macro is evaluated, the input expression is expanded, that is, the macro returns a modified expression. This expansion occurs at parse time when the syntax tree is being built, not when the code is actually executed.

 

 

The following descriptions highlight the difference between macros and functions when they are called or invoked:

  • Function: It takes the input values and returns the computed values at runtime
  • Macro: It takes the input expressions and returns the modified expressions at parse time

In other words, a macro is a custom program transformation. Macros are defined with the keyword as follows:

macro mname 
# code returning expression  
end 

It is invoked as @mname exp1 exp2 or @mname(exp1...