If you are new to Julia programming, this book will help you understand how to write more idiomatic Julia code. We will also focus on describing some of the most useful patterns that are already used in the existing open source Julia ecosystem. That includes Julia's own Base and stdlib packages as the Julia runtime is largely written in Julia itself. We will also reference other packages that are used for numerical computing and web programming. 

For ease of reference, we will organize our patterns by name. For example, the Holy Traits pattern refers to a specific method for implementing traits. The Domain-Specific Language pattern talks about how to build new syntax to represent specific domain concepts. The sole purpose of having a name is just ease of reference.

When we discuss these design patterns in this book, we will try to understand the motivation behind them. What specific problem are we trying to solve? What would be a real-world situation where such a pattern would be useful? Then, we will get into the details of how to solve these problems. Sometimes, there may be several ways to solve the same problem, in which case we will look into each possible solution and discuss the pros and cons.

Having said that, it is important for us to understand the ultimate goal of using design patterns. Why do we want to use design patterns in the first place? To answer this question, it would be useful for us to first understand some key software design principles.