问题:

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?

回答1:

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

回答2:

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!

回答3:

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.