limitWhile (and other limit* methods) problem

[cigaly]

This test will generate ArrayIndexOftOfBoundsException:

@Test
public void limitWhite() {
    Integer array[] = { 1, 2, -1 };
    UnaryOperator<Integer> iterate = x -> array[x];
    Predicate<Integer> filter = x -> x >= 0;

    Seq<Integer> seq1 = Seq.iterate(0, iterate);
    Seq<Integer> seq2 = seq1.limitWhile(filter);
    // After limitWhile seq2 should be { 0, 1, 2 }
    Seq<Integer> seq3 = seq2.map(x -> x + 1);
    // After map seq3 should be { 1, 2, 3 }
    int seq4 = seq3.foldLeft(1, (x, y) -> x * y);
    // Rezult should be 6
    Assert.assertEquals(6, seq4);
}

After filter predicate.test(-1) returns false, iterate.apply(-1) should newer be called.

Here is equivalent code in scala that is working as expected:

val array = Array(1, 2, -1)
def str(x: Int): Stream[Int] = x #:: str(array(x))
val seq1 = str(0)
val seq2 = seq1.takeWhile(x => x >= 0)
val seq3 = seq2.map(x => x + 1)
val seq4 = seq3.foldLeft(1)((x, y) => x * y)

[lukaseder]

Thank you very much for reporting. Will look into this immediately.

[lukaseder]

It might well be that jOOλ could optimise the lazy evaluation of the Seq.iterate() calls (currently passing this through to Stream) to avoid the application of the call array[-1], but in any case, defensive programming would probably suggest this implementation, instead:

UnaryOperator<Integer> iterate = x -> x >= 0 ? array[x] : x;

[cigaly]

You are right, it could be coded that way, still, I would not call that a feature.

[lukaseder]

still, I would not call that a feature.

Well, I didn't, did I? :)

[cigaly]

No, that's true :-)

[tlinkowski]

This issue is a duplicate of #309 :) Fortunately, it's trivial to fix - see https://github.com/jOOQ/jOOL/issues/309#issuecomment-298250192.

[cigaly]

That's correct. With your proposed change thsi is working properly.