Question 1

How do I visualize a finite-state machine in Automat?

Accepted Answer

Use the `automat.viz/view` function in Clojure to generate a visual diagram of states and transitions. This is great for debugging, but note it's not available in ClojureScript, so you'll need to rely on code inspection there.

Question 2

Automat vs Ragel: which is better for Clojure projects?

Accepted Answer

Automat is inspired by Ragel but uses Clojure's functional composition instead of a custom DSL, making it more integrated with Clojure idioms. Choose Automat for Clojure/ClojureScript projects needing composability; Ragel might be better for multi-language or C-based systems.

Question 3

How to handle errors or invalid inputs in Automat FSMs?

Accepted Answer

You can specify error handling by passing an `:error` parameter to `advance` for rejection, or use the `not` operator to define rejection states. This allows custom logic for invalid sequences without crashing.

Question 4

Can Automat be used for parsing JSON or XML?

Accepted Answer

Yes, Automat can define automata for grammar rules, but it's not a dedicated parser library. For complex parsing, consider specialized tools, though Automat works well for token-based validation or sequence matching.

Question 5

How to optimize Automat for high-throughput stream processing?

Accepted Answer

Avoid frequent use of the `$` operator for reductions; instead, use `:start-index` and `:stream-index` to extract data in bulk. Precompile FSMs in Clojure for ClojureScript to reduce startup overhead.

Question 6

What are the limitations when using Automat in ClojureScript?

Accepted Answer

Visualization is not available, and FSM compilation can be slow, impacting startup time. The README recommends precompiling in Clojure via macros to mitigate this for performance-critical apps.

Question 7

How do I attach actions to state transitions in Automat?

Accepted Answer

Use the `$` operator within the automaton definition to associate reducer functions, then specify these functions in the `:reducers` map when compiling the FSM. This allows stateful operations like saving data during transitions.

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