What are the two ways to quote expressions so the code can be manipulated later?

One way is to enclose an expression with :( and ). Another way is to put the code between quote and end keywords. In general, a quote block is used for multiline expressions.

In which scope does the eval function execute the code on?

The eval function evaluates the code in the global scope. So, if it is used from a function inside a module, then the code that is evaluated will be within the scope of the module.

How do we interpolate physical symbols into quoted expressions rather than being misinterpreted as source code?

To interpolate symbols into quoted expressions, create a QuoteNode object and interpolate that object normally.

What is the naming convention for a macro where it defines non-standard string literals?

Non-standard string literals are defined as macros having names ending with _str. For example, when an ip_str macro is defined for an IP address, it can be written: ip"192.168.1.1".

When do we use the esc function?

The esc function is needed to ensure that the quoted expression is evaluated at the call site, which could be in the local scope of a function.

How are generated functions different from macros?

Generated functions have access to the types of the arguments. They are functions by definition so, unlike macros, they do not have access to the source code. Macros operate at the syntax level and do not have any runtime information. Both generated functions and macros are expected to return expressions.

How do we debug metaprogramming code?

Debugging macros can be challenging. It comes down to making sure that the expression being returned is correct. We can use the @macroexpand macro (or the corresponding macroexpand function) to verify results. Also, because a macro or generated function is defined using regular Julia code, the same debugging technique, such as println, can be used.