What’s a simple and canonical way to read an entire file into memory in Scala? (Ideally, with control over character encoding.) The best I can come up with is: scala.io.Source.fromPath(“file.txt”).getLines.reduceLeft(_+_) or am I supposed to use one of Java’s god-awful idioms, the best of which (without using an external library) seems to be: import java.util.Scanner … Read more
I never understood it from the contrived unmarshalling and verbing nouns ( an AddTwo class has an apply that adds two!) examples. I understand that it’s syntactic sugar, so (I deduced from context) it must have been designed to make some code more intuitive. What meaning does a class with an apply function give? What … Read more
I have heard the term “coalgebras” several times in functional programming and PLT circles, especially when the discussion is about objects, comonads, lenses, and such. Googling this term gives pages that give mathematical description of these structures which is pretty much incomprehensible to me. Can anyone please explain what coalgebras mean in the context of … Read more
I’ve seen in many examples that sometimes a Seq is being used, while other times is the List… Is there any difference, other than the former one being a Scala type and the List coming from Java? 5 Answers 5
What is the formal difference between passing arguments to functions in parentheses () and in braces {}? The feeling I got from the Programming in Scala book is that Scala’s pretty flexible and I should use the one I like best, but I find that some cases compile while others don’t. For instance (just meant … Read more
Sealed classes are described in ‘Programming in Scala’, but sealed traits are not. Where can I find more information about a sealed trait? I would like to know, if a sealed trait is the same as a sealed class? Or, if not, what are the differences? When is it a good idea to use a … Read more
All I know about TypeTags is that they somehow replaced Manifests. Information on the Internet is scarce and doesn’t provide me with a good sense of the subject. So I’d be happy if someone shared a link to some useful materials on TypeTags including examples and popular use-cases. Detailed answers and explanations are also welcome. … Read more
Is there any difference between ::: and ++ for concatenating lists in Scala? scala> List(1,2,3) ++ List(4,5) res0: List[Int] = List(1, 2, 3, 4, 5) scala> List(1,2,3) ::: List(4,5) res1: List[Int] = List(1, 2, 3, 4, 5) scala> res0 == res1 res2: Boolean = true From the documentation it looks like ++ is more general … Read more
It’s a sad fact of life on Scala that if you instantiate a List[Int], you can verify that your instance is a List, and you can verify that any individual element of it is an Int, but not that it is a List[Int], as can be easily verified: scala> List(1,2,3) match { | case l … Read more
What is the advantage of using an abstract class instead of a trait (apart from performance)? It seems like abstract classes can be replaced by traits in most cases. 8 Answers 8
