Best resource to learn DSL?

More or less, yep. You can’t really learn DSL per se, DSLs are custom languages that you build yourself. For that you need to know Elixir macros.

I recently started the Metaprogramming Elixir book and I enjoy what I saw and tried so far, so that’s one possible resource for you.

DSL is a concept closely associated with Domain Driven Design, the idea is to have a way to easily express things inside a particular domain. For the technical part, you could learn (like dimitarvp said) Metaprogramming Elixir / Elixir Macro. For the design part, you could learn Domain Driven Design (i would recommend Implementing Domain Driven Design for more easier time of reading DDD).

DSL are used in runtime and compile time. At runtime they help customising the software through scripts or rules. Systems expose ability to customise the functionality/behaviour through the DSLs. For example rules editor in a firebase - Security Rules language  |  Firebase Security Rules . Quite a lot of google cloud services use Common Expression Language - GitHub - cel-expr/cel-spec: Common Expression Language -- specification and binary representation · GitHub 

The complete guide to (external) Domain Specific Languages - Strumenta covers a lot of things about DSLs.

Elixir has metaprogramming through macros which is compile time.Ecto has DSL for simplifying queries for accessing the data. If your use case is writing a compile time DSL - elixir metaprogramming makes it easy. Runtime DSL in elixir needs a lot of things - like interpreter, etc to be implemented.

Implementing a DSL needs grammar to be formalised as language spec.

What are you trying to achieve with DSL in your application? Is it runtime or compile time ?

That book is generally highly recommended, but if you want something shorter to start off with there’s also Saša Jurić’s blog series starting here . I haven’t gone through it yet, but I’ve found Jurić’s other writings lucid.

Thank you such detailed reply.

My use case only involves writing some macros to help write other code easier at compile time.

Thank you. Like @crispinb pointed out Sasa Juric’s blog post series is a good place to start.

Metaprogramming Elixir -Metaprogramming Elixir: Write Less Code, Get More Done (and Have Fun!) by Chris McCord is a book which is completely about Metaprogramming. You will find a coupon code in this forum for most of the elixir books.

One thing about metaprogramming is - it may not be needed most of the time. Using import and functions might solve the problem. Chapter 6 of Metaprogramming Elixir book explains more about it.

I learnt a lot by searching about how elixir, ecto and phoenix use defmacros in their code base:

• Phoenix - Repository search results · GitHub
• Ecto - Repository search results · GitHub