How can I access the last result in Scala REPL?

Question

In python REPL I can do things like:

>>> [1,2,3,4]
[1, 2, 3, 4]
>>> sum(_)
10

In clojure REPL I can do this:

user=> "Hello!"
"Hello!"

user=> *1
"Hello!"

Is there is something like this in Scala REPL?

score 42 · Accepted Answer · answered Aug 15 '12 at 15:30

42

Yes, you can use dot notation to refer to the last result:

scala> List(1,2,3,4)
res0: List[Int] = List(1, 2, 3, 4)

scala> .sum
res1: Int = 10

answered Aug 15 '12 at 15:30

om-nom-nom

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This doesn't work for something like `scala> 4 + 5` and then `scala> . * 3`. Please provide more detail as my google search for 'scala .' is not helping. – Merlin Oct 09 '19 at 17:44
I should add it does work for something like a shell command result: `scala> :sh ls -l` and then `scala> .lines foreach println` – Merlin Dec 28 '19 at 17:20

score 8 · Answer 2 · answered Aug 15 '12 at 18:27

You can refer to the previous output as resN for some N. You've probably noticed that in the Scala REPL, results are printed in the form resN: Type = value:

Welcome to Scala version 2.9.1.final (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_24).
Type in expressions to have them evaluated.
Type :help for more information.

scala> List(1,2,3,4)
res0: List[Int] = List(1, 2, 3, 4)

scala> "Hello!"
res1: java.lang.String = Hello!

Well, that resN is a real variable name. In this example, you can refer to the list as res0 and the string as res1 for (at least as far as I know) as long as the REPL is open:

scala> (res0.toString + res1) toLowerCase
res2: java.lang.String = list(1, 2, 3, 4)hello!

score -1 · Answer 3 · answered Aug 15 '12 at 22:50

-1

I normally just hit the ↑ key to bring back the last line of code and carry on typing. This has the advantage of keeping the whole expression together for easy cutting-and-pasting or editing later.

answered Aug 15 '12 at 22:50

Luigi Plinge

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How can I access the last result in Scala REPL?

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