Scala: Iterate through list of ranges

Question

I have a list of 3 elements. I want to create range from each of them and iterate through all possible combinations.

What I need to re-write to be able operate with different amount of elements in initial list:

val el = List(5, 4, 7)
(0 to el(0)).map { e0 => 
(0 to el(1)).map { e1 => 
(0 to el(2)).map { e2 => 
doSmth(List(e1,e2,e0))
}}}

It should be simple task. Just curious how to google it...

I'm not sure what you're asking for makes sense since you'd have to know at compile-time how many arguments doSmth takes, meaning that you'd have to know how low el is at compile-time too. — dhg
– dhg, Commented Mar 26, 2015 at 19:32

Ben Reich · Accepted Answer · 2015-03-26 19:32:31Z

2

You can pretty easily get all combinations using recursion:

def combos(list: List[Int]): List[List[Int]] = list match {
   case hd::tl => combos(tl).flatMap{ combo => (0 to hd).map(_ :: combo) }
   case Nil => List(List())
}

answered Mar 26, 2015 at 19:32

Ben Reich

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