- About Scala
- Documentation
- Code Examples
- Software
- Scala Developers
Creating map from list of pairs
Hi. If I have a list of pairs. What's the best way to initialize a map
from them? Right now I'm doing this:
val m = Map() ++ pairs
Secondly, is there a nicer way to turn an Option into a Set than this:
def toSet[T](o : Option[T]) : Set[T] = {
o match {
case Some(some) => Set(some)
case None => Set()
}
}
Every time I write one of these utility functions I find out there's a
more elegant, built-in way to do it.
Thanks!
Dave
Re: Creating map from list of pairs
Secondly, is there a nicer way to turn an Option into a Set than this:
def toSet[T](o : Option[T]) : Set[T] = {
o match {
case Some(some) => Set(some)
case None => Set()
}
}
How about this:
o.map(Set(_)).getOrElse(Set())
Re: Creating map from list of pairs
Map(List(Pair(1, 2), Pair(3, 4)): _*)
--Bryan
On Mon, Jan 12, 2009 at 10:59 AM, Dave Ray <daveray [at] gmail [dot] com> wrote:
Re: Creating map from list of pairs
That's what I always do.
Thanks,
David
Re: Creating map from list of pairs
Could someone explain why the final ": _*" is needed, and what it means
exactly?
(The error if I omit it:
:4: error: type mismatch;
found : List[(Int, Int)]
required: (?, ?)
)
O/H David Pollak έγραψε:
>
> That's what I always do.
>
> Thanks,
>
> David
>
> On Jan 12, 2009 8:25 AM, "Bryan" > wrote:
>
> I don't know how great of a solution this is, but you could do
> something like:
>
> Map(List(Pair(1, 2), Pair(3, 4)): _*)
>
> --Bryan
>
> On Mon, Jan 12, 2009 at 10:59 AM, Dave Ray > wrote: > > Hi. If I have a list of ...
>
Re: Creating map from list of pairs
Dimitris Andreou wrote:
> Could someone explain why the final ": _*" is needed, and what it means
> exactly?
>
> (The error if I omit it:
> :4: error: type mismatch;
> found : List[(Int, Int)]
> required: (?, ?)
> )
If I'm reading the book correctly it means to treat the argument as a
sequence of arguments (a vararg list) instead of a single argument of
type Seq[(Int, Int)].
Derek
Re: Creating map from list of pairs
def varargfunc( argument : T* ) ...
On Mon, Jan 12, 2009 at 12:52 PM, Dimitris Andreou <jim [dot] andreou [at] gmail [dot] com> wrote: