7 languages in 7 weeks: Scala day 2

Day two is all about collections. Forcing the typical Java developer (me) to think about iteration in a different way.

Exercise 1 is to take a List of strings and add up the number of characters using the fold left function. There is a very similar example in the book so I think the author is just checking you are paying attention:

listOfStrings.foldLeft(0)((sum, value) => sum + value.length)

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Exercise 2 introduces you to Traits by asking you to develop a trait that has a method which censors a string by substituting words in a string. The words to substitute and what to substitute them with should be stored in a Map.

	trait Censor {
	var alternatives = Map("Shoot" -> "Pucky", "Darn" -> "Beans")
	def censor(input : String) : String = {
	var toReturn = input
	alternatives.foreach( entry => toReturn = toReturn.replace(entry._1, entry._2))
	toReturn
	}
	}

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Then create a version that loads the substitutions from a file:

	import scala.io.Source._
	trait CensorFromFile extends Censor {
	val curses =
	fromFile("day2/curses")
	.getLines()
	.map(_.split("="))
	.map(fields => fields(0) -> fields(1)).toList
	alternatives = Map(curses : _*)
	}

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I chose to extend the trait and populate the alternatives field. Spending all my days writing Java what I ended up producing looks very alien to me. It works (I think) something like this:

• Open and read a file using the library method fromFile
• Get the lines of the file one by one using getLines
• Map each like to an Array by splitting the like with the = sign (the file is key value pairs like a Java properties file)
• Map the array to a tuple then turn it into a list
• Construct a map from the List of tuples

And done! Looks a lot nicer than it sounds! The full source code is available on my github.