CODEWITHSUNDEEP
scalavariadic-functions
GentlemanHal
GentlemanHal

Reputation: 354

Passing a individual arguments AND a Seq to a var-arg function

I know it's possible to pass individual arguments to a vararg function and it's possible to pass a seq using :_* but is it possible to pass both?

for example:

scala> object X { def y(s: String*) = println(s) }
defined module X

scala> X.y("a", "b", "c")
WrappedArray(a, b, c)

scala> X.y(Seq("a", "b", "c"):_*)
List(a, b, c)

scala> X.y("a", Seq("b", "c"):_*)
<console>:9: error: no `: _*' annotation allowed here
(such annotations are only allowed in arguments to *-parameters)
       X.y("a", Seq("b", "c"):_*)
                             ^

Edit: In Scala 2.10 (in case that matters)

Upvotes: 6

Views: 3504

Answers (2)

Randall Schulz
Randall Schulz

Reputation: 26486

If you look around in the Scala standard library you'll find this sort of pattern in places:

def doIt(arg: Thing)
def doIt(arg1: Thing, arg2: Thing, moreArgs: Thing*)

You can see this, e.g., in Set.+(...). It allows you to have any number of arguments without ambiguity in the overloads.

Addendum

Proof of concept:

scala> class DI { def doIt(i: Int) = 1; def doIt(i1: Int, i2: Int, iMore: Int*) = 2 + iMore.length }
defined class DI

scala> val di1 = new DI
di1: DI = DI@16ac0be1

scala> di1.doIt(0)
res1: Int = 1

scala> di1.doIt(1, 2)
res2: Int = 2

scala> di1.doIt(1, 2, 3)
res3: Int = 3

scala> di1.doIt(1, 2, List(3, 4, 5): _*)
res4: Int = 5

Upvotes: 3

om-nom-nom
om-nom-nom

Reputation: 62855

Hacky but this should work well: 

X.y(Seq("a") ++ Seq("b", "c"):_*)

Upvotes: 5

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