Idiomatic Scala List Comprehension - first item that matches

Question

Folks, I've been writing some code in Scala lately to teach myself the language and in some recent experiments, I've used an NLP library to produce a set of part-of-speech tagged words from a user's input.

I want to write a function that gives me the first verb in the sentence. If there are no verbs, then I want to assume that the first word in the set is the verb (e.g. if the player just typed "who" or "uptime" , those are considered verbs by my game).

The following is a block of code so ugly only a mother could love, and it stinks of imperative programming and I want to refactor it into something more like idiomatic Scala, ideally something that doesn't have a single "if" statement in it.

def firstVerb = {
    if (words.size == 1)
        words.head.value
    else {
        val outWords = words.filter( word => word.pos == Verb)
        if (outWords == Set.empty) 
            words.head.value
        else
            outWords.head.value 
    }
}

The "words" variable is of type ListBuffer[EnrichedWord], where EnrichedWord is my class that contains a part of speech (pos, contains case objects like Verb, Noun, etc) and the original word (value).

Any guidance you Scala geniuses can provide in refactoring this butt-ugly code would be fantastic.

Answer 1

This additionally handles the case when words is empty, try it:

words.find(_.pos == Verb).orElse(words.headOption).map(_.value).getOrElse("")

If you are sure words will never be an empty Set, this one is simpler:

words.find(_.pos == Verb).getOrElse(words.head).value

BTW if you are using HashSet the notion of some element being first doesn't really make sense. If each element represents a word in a sentece, it should have been a List or a Seq.

Answer 2

The canonical (point-free) version is probably:

words find(_.pos == Verb) orElse words.headOption map _.value getOrElse ""

Another option is:

(words.find(_.pos == Verb) ++ words.take(1)).take(1).map(_.value).mkString