Scala: Array, List, Seq to argument function

Question

How can this be automated? (Insert the elements of the array into the arguments of the function)


def func(d1: Boolean, d2: Boolean, d3: Boolean, d4: Boolean) = ???

val data = Array(true, true, false, false)

func(
  data(0),
  data(1),
  data(2),
  data(3)
)

Scala has an `apply` method that does this doesn't it? In most languages (that I know at least), the function that achieves this is called `apply`. — Carcigenicate, Jul 15 '17 at 15:35
@Carcigenicate `apply` is used for `object`s (types, really). One could create a helper object that does something similar to tuple unwrapping in Python, but otherwise this isn't going to get much cleaner. — erip, Jul 15 '17 at 15:43

score 2 · Answer 1 · answered Jul 15 '17 at 16:06

2

If I undestand your question correctly:

def func(d: Boolean*) = {
  d.map( if (_) "yes" else "no" ).foreach(println)
}

val data = Array(true, true, false, false)

func(data: _*)
yes
yes
no
no

answered Jul 15 '17 at 16:06

Leo C

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score 1 · Answer 2 · answered Jul 15 '17 at 16:05

1

You can use the 'splat' operator with a varargs argument:

def func(args : Boolean*) = {
  args foreach println
}

val data = Array(true, true, false, false)

func(data: _*)

answered Jul 15 '17 at 16:05

sheunis

1,494
11
10

score 0 · Answer 3 · answered Jul 16 '17 at 09:18

0

If you manage to convert your list to a tuple:

scala> def func(d1: Boolean, d2: Boolean, d3: Boolean, d4: Boolean) = s"$d1 $d2 $d3 $d4"
func: (d1: Boolean, d2: Boolean, d3: Boolean, d4: Boolean)String

scala> val ff = func _
ff: (Boolean, Boolean, Boolean, Boolean) => String = $$Lambda$1151/1744486549@5a13f1f7

scala> val data = (true,false,true,true)
data: (Boolean, Boolean, Boolean, Boolean) = (true,false,true,true)

scala> ff.tupled(data)
res8: String = true false true true

answered Jul 16 '17 at 09:18

Assen Kolov

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`data` is a tuple, not an `Array` or `Seq` – Alexander Azarov Jul 16 '17 at 09:37
@AlexanderAzarov My post begins with `If you manage to convert your list to a tuple` – Assen Kolov Jul 16 '17 at 09:42
I assume OP is able to search SO for questions with answers. – Assen Kolov Jul 16 '17 at 09:52
Oh, c'mon. OP would not register and ask the question, if he/she could search SO – Alexander Azarov Jul 16 '17 at 10:42

Alexander Azarov · Answer 4 · 2017-07-16T09:48:19.283

0

Make a "tupled" function, just like in Assen Kolov's answer:

def func(d1: Boolean, d2: Boolean, d3: Boolean, d4: Boolean) = ???

val f = func _

then create a tuple from your Seq. This answer shows how to do it in a type-safe way.
And call your function f with a tuple argument.

edited Jul 16 '17 at 09:48

answered Jul 16 '17 at 09:40

Alexander Azarov

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Scala: Array, List, Seq to argument function

4 Answers4