Generating Less Code by Walking the AST
Explore how to generate less code in Elixir while maintaining an expressive HTML Domain-Specific Language. Learn to use Macro.prewalk and Macro.postwalk functions to traverse and transform the Abstract Syntax Tree, replacing the need to write hundreds of individual macros. Understand pattern matching on AST nodes to dynamically convert them into macro calls, streamlining DSL creation and improving code maintainability.
The trial terminal
Use this terminal to test and execute the commands provided in the lesson:
Generating less code while maintaining the DSL
Our Html module is clear and concise, but we had to generate over a hundred macros to make it work. Wouldn’t it be nice to generate less code but still maintain our expressive DSL where all tags can be used as macro calls? Let’s make it happen.
The idea of maintaining the DSL without generating all HTML macros sounds impossible, but step back and remember that Elixir provides full AST access. For example, open up an iex prompt and quote a few arbitrary HTML DSL expressions, and let’s look at the results. Do not load Html module since we are just quoting raw expressions outside the context of our library for this example by executing the following commands:
iex> ast = quote do
...> div do
...> h1 do
...> text "hello"
...> end
...> end
...> end
# Output: {:div, [], [[do: {:h1, [], [[do: {:text, [], ["Hello"]}]]}]]}
It looks pretty ...