How do I change this code to be functional programming in scala?

Question

I'm new to functional programming and as I'm reading this book. It basically says that if you code contains "var" it means that you're still doing in a imperative way. I'm not sure how do I change my code to be functional way. Please suggests.

So basically what this code does is to processText some text and use regular expression to extract a particular text from "taggedText" and add that to a list and convert the list to json.


    val text = params("text")
    val pattern = """(\w+)/ORGANIZATION""".r

    var list = List[String]()
    val taggedText = processText(text)
    pattern.findAllIn(taggedText).matchData foreach {
      m => list ::= m.group(1)
    }

    pretty(render(list)) // render to json

Luigi Plinge · Accepted Answer · 2012-05-16 22:34:42Z

7

Try replacing the middle section with

val list = pattern.findAllIn(taggedText).matchData.map(m => m.group(1)).toList

You can write m => m.group(1) as _.group(1) if you want.

answered May 16, 2012 at 22:34

Luigi Plinge

51.2k21 gold badges117 silver badges185 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Dave Griffith Over a year ago

As a more general rule, building up a data structure functionally Scala usually turns out to be best done using either "map", "flatMap" or "fold", in increasing order of difficulty. There are a few variants on those ("collect", "groupBy", "foldMap") that may be handy in certain cases, but as a general rule "map", "flatMap" and "fold" get you where you need to go.

tgr Over a year ago

If those methods are new to you I recommand yield. You can use a for comprehension and yield the result collection. Behind the scenes yield is translated to map, flatmap, filter and so on.

Collectives™ on Stack Overflow

How do I change this code to be functional programming in scala?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related