.filter(_.nonEmpty).map(_.get)

[Andy C]

Hi,

I wonder if there is a shortcut for ".filter(_.nonEmpty).map(_.get)". I quite often need to create a list of objects of a initial sequence of data where not all elements results in newly created objects (I use None for that). At that point I want to filter out "weeds" and expose "fruits" from such a sequence. I currently use ".filter(_.nonEmpty).map(_.get)" but wonder if there is a better way of achieving it.

Thanks in advance,
Andy

[Haoyi Li]

Doesn't .flatten do this for you? E.g. It takes seq[option[t]] and turns it into seq[t] iirc

Sent from my Windows Phone

---

From: Andy C
Sent: 6/3/2013 8:27 PM
To: scala-user
Subject: [scala-user] .filter(_.nonEmpty).map(_.get)

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[Vlad Patryshev]

If you are using 2.8, .flatMap(_.toList); otherwise just .flatten

Thanks,
-Vlad

[Brian Maso]

collect { case Some(x) => x } also works, though I like flatten better.

On Mon, Jun 3, 2013 at 5:27 PM, Andy C <andy.c...@gmail.com> wrote:

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[Som Snytt]

filter out "weeds"

My contribution is that the usual word is "chaff", but "tares" will convey "weeds" more specifically.

To wit,
http://en.wikipedia.org/wiki/Chaff
http://en.wikipedia.org/wiki/Parable_of_the_Tares

"flatten" really does mean to remove the "chaff", or useless husk that encases the wheat (when there is a berry, or None otherwise).

On Mon, Jun 3, 2013 at 5:27 PM, Andy C <andy.c...@gmail.com> wrote:

[Odd Möller]

I would suggest .collect { case Some(x) => x.get } for this, since it combines the filtering and the maping into one sweet operation.

Greetings

Odd Möller

[Alec Zorab]

.collect { case Some(x) => x}, surely?

[Odd Möller]

Of course :)

Thanks!

//Odd

[Alexandru Nedelcu]

On Tue, Jun 4, 2013 at 3:27 AM, Andy C <andy.c...@gmail.com> wrote:

I wonder if there is a shortcut for ".filter(_.nonEmpty).map(_.get)". I quite often need to create a list of objects of a initial sequence of data where not all elements results in newly created objects (I use None for that). At that point I want to filter out "weeds" and expose "fruits" from such a sequence. I currently use ".filter(_.nonEmpty).map(_.get)" but wonder if there is a better way of achieving it.

All alternatives:

  scala> Seq(Some(1), Some(2), None).filter(_.nonEmpty).map(_.get)
  res1: Seq[Int] = List(1, 2)

  scala> Seq(Some(1), Some(2), None).foldLeft(Seq.empty[Int])((a,e) => e.map(a :+ _).getOrElse(a))
  res2: Seq[Int] = List(1, 2)

  scala> Seq(Some(1), Some(2), None).collect { case Some(x) => x }
  res3: Seq[Int] = List(1, 2)

  scala> for (opt <- Seq(Some(1), Some(2), None); e <- opt) yield e
  res4: Seq[Int] = List(1, 2)

  scala> Seq(Some(1), Some(2), None).flatMap(x => x)
  res5: Seq[Int] = List(1, 2)

  scala> Seq(Some(1), Some(2), None).flatten
  res6: Seq[Int] = List(1, 2)