Is there a concise, idiomatic way to create an order-preserving map from a Javaslang / Vavr List? List.toMap() returns a plain HashMap, so that doesn't do it. What I have right now is something like this --
listOfKeys.foldLeft(
LinkedHashMap.<Key, Value>.empty(),
(m, k) -> m.put(k, valueFor(k))
);
-- but this seems more verbose than necessary, and possibly less efficient as well.
The Value.collect method (inherited by List) is usually used for this purpose, which is analogous to the Java 8 Stream's collect method. It takes a collector to perform a mutable reduction (see note). Vavr LinkedHashMap provides a static collector() method, so you can use that to get an instance to a collector which will collect to a LinkedHashMap.
listOfKeys.map(key -> new Tuple2<>(key, valueForKey(key)))
.collect(LinkedHashMap.collector());
I'm not sure how it will perform compared to your solution though, I don't think it will have a difference in performance, but as an added bonus it's compatible with the JDK collectors, so you can use that to collect to JDK collections easily.
* Note that since the Vavr collections are immutable, mutable reduction isn't actually mutable in this context.
It seems that there is a toLinkedMap() now.
Hope it can help here.
