Question 1

How to use ordered maps for consistent JSON output in Clojure?

Accepted Answer

Ordered maps ensure keys are serialized in insertion order, which is useful with JSON libraries that preserve map order. Replace hash-map with ordered-map in your data structures, and serialize as usual for predictable key sequences.

Question 2

Ordered vs sorted maps in Clojure: when to use each?

Accepted Answer

Use ordered maps for maintaining insertion order, such as in UI rendering or logging sequences. Use sorted maps (e.g., sorted-map) when you need elements ordered by keys, like for alphabetical sorting or range queries, as ordered only preserves insertion order.

Question 3

How to convert a regular Clojure map to an ordered map?

Accepted Answer

Use the into function with an ordered-map, e.g., (into (ordered-map) {:a 1 :b 2}). This preserves the order of the source sequence if it has one, otherwise, it follows the insertion order from the sequence.

Question 4

Does the ordered library support nested ordered collections?

Accepted Answer

Yes, you can nest ordered sets and maps, but order is preserved per individual collection, not globally. For example, an ordered map can contain ordered sets, but traversal order depends on each collection's insertion history.

Question 5

What are the performance costs of using ordered sets over hash sets?

Accepted Answer

Ordered sets may have higher memory usage and slower operations due to maintaining order, similar to LinkedHashSet in Java. For performance-critical code, benchmark with your data size and access patterns to assess overhead.

Question 6

How to merge two ordered maps while preserving order?

Accepted Answer

Use merge or into, but order depends on the sequence of operations. For predictable results, merge them in a specific order, e.g., (into (ordered-map) (concat map1 map2)) to maintain the concatenated insertion sequence.

Question 7

Can ordered collections be used with core.async or other concurrency libraries?

Accepted Answer

Yes, but since they are not thread-safe by default, you need to manage synchronization externally. Wrap them in atoms or use agents to ensure safe concurrent access in frameworks like core.async.

Ordered

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