Exit for loop as soon as condition satisfied

Question

The following code hangs the repl:

(
  for {
    i <- 1 to 1000000
    j <- 2 to 1000000
    if i * i == j
  } yield i -> j
).take(1)

It seems the for expression is eagerly evaluated. Any solutions?

This could answer your question: http://stackoverflow.com/questions/2742719/how-do-i-break-out-of-a-loop-in-scala — Phillip Trent, Jun 19 '15 at 10:22

bjfletcher · Answer 1 · 2015-06-19T11:24:28.900

1

I'd turn that into a stream:

(
    for {
        i <- Stream.range(1, 1000000)
        j <- Stream.range(2, 1000000)
        if i * i == j
    } yield i -> j
).take(1)

edited Jun 19 '15 at 11:24

answered Jun 19 '15 at 10:39

bjfletcher

make that `Stream.range(1,10000000)` and you will avoid creating a gigantic `(1 to 1000000)` `Range` instance. – Chirlo Jun 19 '15 at 11:20

1 Answers1