Macros are defined in a similar way to how functions are defined, except that the macro keyword is used instead of the function keyword.

We should also keep in mind that a macro must return expressions. Let's create our first macro. This macro returns an expression object that contains a for loop, as follows:

macro hello()
    return :(
    for i in 1:3
        println("hello world")
    end
    )
end

Invoking the macro is as easy as calling it with the @ prefix. Refer to the following code:

Unlike functions, macros may be called without using parentheses. So we can just do the following:

Fantastic! We have now written our first macro. While it does not look very exciting, because the code being generated is just a static piece of code, we have learned how to define macros and run them.

Next, we will learn how to pass arguments to macros.