FOR LOOP Multiple Generators

Question

Problems understanding how the code below works. I am new to Scala and have been learning the language for 2 weeks now.

for (i <- 1 to 3; j <- 1 to 3) print((10 * i + j) + " ")

it prints 11 12 13 21 22 23 31 32 33. Does it assign each value in turn i.e.

i = 1

j = 0

or does the values get assigned each time it loops i.e.

i = 1

j = 1

Thanks

Answer 1

It's just nested loop for j. So, for each assigned value of i, all values of j are iterated.

for (i <- 1 to 3) {
  for (j <- 1 to 3) {
    print((10 * i + j) + " ")
  }
}

Because a for loop expands to foreach, your code is also equivalent to:

(1 to 3).foreach { i =>
  (1 to 3).foreach { j =>
    print((10 * i + j) + " ")
  }
}

Maybe in this form, it's more easy to see.