Hands-On Design Patterns and Best Practices with Julia

Understanding the macro expansion process

By convention, every macro must return an expression. The process of taking one or more expressions and returning a new one is called macro expansion. Sometimes, it helps to see the expression being returned without actually running the code. We can use the @macroexpand macro for that purpose. Let's try to use it for the @hello macro that we defined earlier in this section:

There are several things to note from this output:

• The i variable was renamed rather oddly: #67#i. This is done by the Julia compiler to ensure hygiene, which we will discuss later in this chapter. Macro hygiene is an important ...