CODEWITHSUNDEEP
scala
amrita
amrita

Reputation: 133

Scala for loop multiple counters

I'm new to Scala, and I'm trying to convert this for loop from Java:

for(int x=1, y=2; x<=5; x++, y+=2)
    System.out.println(x+y);

I'm trying to zip the values in Scala since I can't find a way to have multiple counters which are non-nested:

val a = Seq(1 to 5)
val b = Seq(2 to 10 by 2)
for((x,y) <- a.zip(b))
  println(x+y)

But the above code is giving this error:

type mismatch; found: scala.collection.immutable.Range required: String

Does anyone know how to fix this? I would prefer to do with for loop only, not while loop.

Upvotes: 2

Views: 760

Answers (3)

Ricardo
Ricardo

Reputation: 4328

In your example you want x to range from 1 to 5 and y is always 2*x. Using for loops is easy for those coming from Java:

for(x <- 1 to 5; y = x*2) {
  println(s"x = $x, y = $y, x+y = ${x+y}")
}

Here is solution to a more generic problem - iterating over elements in a collection using multiple counters (=indices or pointers), like if you want to compare each 2 pairs:

val c = List("a", "b", "c", "d") //or any collection 
val end = c.length - 1 
for(i <- 0 to end-1; j <- i+1 to end)
  //compare or operate with each pair
  println(c(i)+c(j))

... prints:

ab
ac
ad
bc
bd
cd

Upvotes: 0

Tanjin
Tanjin

Reputation: 2452

Try this, no need to wrap the Range in a Seq:

val a = 1 to 5
val b = 2 to 10 by 2
for(
  (x,y) <- a.zip(b)
) 
println(x+y)

Upvotes: 2

jwvh
jwvh

Reputation: 51271

You might try . . .

((1 to 5) zip (2 to 10 by 2)).foreach(x => println(x._1+x._2))

Because Scala for comprehensions are sufficiently different from for() loops in other languages, it's often a good idea for beginners to avoid them until they've gained a sufficient knowledge of map, flatMap, and foreach.

Upvotes: 2

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