How does Scala's groupBy identity work?

Question

I was browsing around and found a question about grouping a String by it\'s characters, such as this:

The input:

\"aaabbbccccdd\"
         


        

Answer 1

First, let's see what happens when you iterate over a String:

scala> "asdf".toList
res1: List[Char] = List(a, s, d, f)

Next, consider that sometimes we want to group elements on the basis of some specific attribute of an object.

For instance, we might group a list of strings by length as in...

List("aa", "bbb", "bb", "bbb").groupBy(_.length)

What if you just wanted to group each item by the item itself. You could pass in the identity function like this:

List("aa", "bbb", "bb", "bbb").groupBy(identity)

You could do something silly like this, but it would be silly:

List("aa", "bbb", "bb", "bbb").groupBy(_.toString)