scala Iterable#map vs. Iterable#flatMap

Question

What is the difference between the `map` and `flatMap` functions of `Iterable`?

Accepted Answer

Here is a pretty good explanation:

http://www.codecommit.com/blog/scala/scala-collections-for-the-easily-bored-part-2

Using list as an example:

Map's signature is:

```
map [B](f : (A) => B) : List[B]
```

and flatMap's is

```
flatMap [B](f : (A) => Iterable[B]) : List[B]
```

So flatMap takes a type [A] and returns an iterable type [B] and map takes a type [A] and returns a type [B]

This will also give you an idea that flatmap will "flatten" lists.

```
val l  = List(List(1,2,3), List(2,3,4))

println(l.map(_.toString)) // changes type from list to string
// prints List(List(1, 2, 3), List(2, 3, 4))

println(l.flatMap(x => x)) // "changes" type list to iterable
// prints List(1, 2, 3, 2, 3, 4)
```

Solution