_14_summary.md

• Elixir compilation is 3 phased

  • Parsing, Expansion, Byte code generation
  • Expansion happens recursively
  • Metaprogramming in Elixir happens in the Expansion phase

• defmacro

  • is called during the expansion phase of the Elixir compiler
  • receives it's arguments as an AST
  • results are exanded & inlined

• Macros

  • are hygienic by default
  • but you can disable that (if you need to)

• quote

  • creates an AST fragment
  • A tree of 3 element tuples (operation, context, arguments)

• unquote

  • wraps existing terms for injection into an AST fragment

• WTF is going on?

  • Macro.expand, Macro.expand_once & Macro.to_string are your friends