Parameters List (*) in Scala

[Edmondo Porcu]

Dear all,

I have a problem with parameters list in Scala.... I obtain a type mismatch which I am not expecting:

def filterYears(toSkip: Range*) = skipSomething(12,toSkip);

def filterMonths(toSkip: Range*) = skipSomething(1,toSkip)

private def skipSomething( multiplier:Int,toSkip:Range*){}

Results in the following compiler error:

error: type mismatch;

found   : Range*

required: Range

def filterYears(toSkip: Range*) = skipSomething(12,toSkip);

error: type mismatch;

found   : Range*

required: Range

def filterMonths(toSkip: Range*) = skipSomething(1,toSkip)

What is the reason for that?

Best Regards

[Sciss]

varargs (the last parameter with an asterisk) allow you to _call_ that method with variable arguments, but inside the method body they appear collected into a sequence under the name of the argument (otherwise how would you distinguish them?). so you are trying to call a method skipSomething( _: Int, _: Seq[Range]). you can expand a sequence to varargs again for a subsequent call through the special type _* :

def filterYears(toSkip: Range*) = skipSomething(12,toSkip: _*)

best, -sciss-

[Erik Osheim]

On Thu, Jan 12, 2012 at 06:07:21PM +0100, Edmondo Porcu wrote:
> error: type mismatch;
> found : Range*
> required: Range

Hi Edmondo,

I thin you want to use :_*

For instance:

def foo(ns:Int*) = ns.sum
def bar(ns:Int*) = foo(ns:_*) * 2

Hope this helps!

-- Erik

[HamsterofDeath]

Am 12.01.2012 18:11, schrieb Sciss:
> varargs (the last parameter with an asterisk) allow you to _call_ that method with variable arguments, but inside the method body they appear collected into a sequence under the name of the argument (otherwise how would you distinguish them?). so you are trying to call a method skipSomething( _: Int, _: Seq[Range]). you can expand a sequence to varargs again for a subsequent call through the special type _* :
>
> def filterYears(toSkip: Range*) = skipSomething(12,toSkip: _*)

and that one goes into the cheat sheet, too