How to build a collection based on Cartesian product of all elements of other collections?
collections, java, scala
Solution
I am not sure about the best practice, but one way you could accomplish this is to us a use a `for` comprehension to create the collection you are looking for:
val signals = List[String](...)
val states = List[SignalState](...)
for(signal <- signals; state <- states) yield new SignalAndState(signal, state)
That should yield a `List[SignalAndState]` with all the elements
Alternately, you could use a `flatMap` and `map` to accomplish the same result, like:
signals flatMap ( signal => states map ( state => new SignalAndState(signal, state)))
Problem
Can You share any good solution for creating immutable collection in Scala based on full iteration of items in several arrays/another collections? E.g. in Java you can use: ``` List<String> signals = ...; List<SignalState> states = ...; List<SignalAndState> result = new ArrayList<~>(signals.size() * states.size()); for (String signal: signals) { for (SignalState state: states) { // some if() condition or process() function can be here result.add(new SignalAndState(signal, state)) } } ``` What are the best practices of building smth like this using Scala? The same approach (using for() in for()) is bad idea, I think, and is not compatible with object-functional nature of Scala language at all.