CODEWITHSUNDEEP
scalaparameters
LoranceChen
LoranceChen

Reputation: 2574

Scala by name repeated parameter

I want to do this, the parameter is lazy and repeatable:

def f(actions: (=> Try[String])*) = {
  actions.map{x =>
    if(x.isFailure) throw new Exception()
    ...
  }
}

So, I can evaluate parameter with this:

f(Try("a"), Try("b"), Try[String](new Exception()), Try({print("something"); "d"}))

The print("something") never be executed because parameters is lazy.

rather then:

def f(actions: (() => Try[String])*) = ???
f(() => Try("a"),() => Try("b"),() => Try[String](new Exception()), () => Try({print("something"); "d"}))

It just writing feeling boring.
Is Scala support the first one?

Upvotes: 0

Views: 101

Answers (2)

HTNW
HTNW

Reputation: 29193

Wrap by name parameters as so:

implicit class ByNameWrapper[+A](a: => A) { def get: A = a }

And define your method as

def f(actions: ByNameWrapper[Try[String]]*) {
  ...
}

Usage is the same as normal by-name parameters:

f(Try { throw new Exception }, Try { println("a"); "b" })

Upvotes: 3

som-snytt
som-snytt

Reputation: 39587

It's coming to dotty. Or it's already in dotty.

https://github.com/lampepfl/dotty/issues/499

Upvotes: 1

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