@Test
public void testFlattenResult() {
List<Integer> list = List.list(1, 2, 3, 4, 5, 0, 6, 7, 8, 9);
List<Double> list2 = List.flattenResult(list.map(inverse));
assertEquals(
"[1.0, 0.5, 0.3333333333333333, 0.25, 0.2, 0.16666666666666666, 0.14285714285714285, 0.125, 0.1111111111111111, NIL]",
list2.toString());
}
@Test
public void testExists() throws Exception {
List<Integer> list = List.list(1, 2, 3, 4, 5, 6, 7, 8);
assertTrue(list.exists(x -> x < 4));
assertFalse(list.exists(x -> x < 1));
assertTrue(list.exists(x -> x > 0));
assertTrue(list.exists(x -> x > 4));
}
@Test
public void testExistsEmpty() throws Exception {
List<Integer> list = List.list();
assertFalse(list.exists(x -> x < 4));
assertFalse(list.exists(x -> x < 1));
assertFalse(list.exists(x -> x > 0));
assertFalse(list.exists(x -> x > 4));
}
/**
* This test demonstrates the known problem of creating streams from mutable structures.
*
* <p>Some of the ways streams created in this way can fail is: - weak stream references getting
* garbage collected - underlying mutable data structure changes - iterator gets updated (e.g.
* iterator used to create 2 different streams).
*/
@Test(expected = ConcurrentModificationException.class)
public void iterableStreamWithStructureUpdate() {
java.util.List<Integer> list = List.list(1, 2, 3).toJavaList();
Stream<Integer> s1 = Stream.fromIterable(list);
int x = s1.head();
list.remove(1);
Stream<Integer> s2 = s1.tail()._1();
x = s2.head();
}
/*
* A simple recursive solution
*/
public static Tuple<List<Integer>, RNG> ints(int count, RNG rng) {
return count == 0 ? new Tuple<>(List.list(), rng) : intsHelper(count, rng);
}
/*
* A tail-recursive stack safe solution. Note that the output list is in
* reverse order, but this is perfectly acceptable regarding the requirements.
*/
public static Tuple<List<Integer>, RNG> ints2(int count, RNG rng) {
return ints2(count, rng, List.list()).eval();
}
/*
* In `sequence`, the base case of the fold is a `unit` action that returns
* the empty list. At each step in the fold, we accumulate in `acc` and `f` is
* the current element in the list. `map2(f, acc)(_ :: _)` results in a value
* of type `Rand[List[A]]` We map over that to prepend (cons) the element onto
* the accumulated list.
*
* We are using `foldRight`. If we used `foldLeft` then the values in the
* resulting list would appear in reverse order. It would be arguably better
* to use `foldLeft` followed by `reverse`. What do you think?
*/
public static <A> Rand<List<A>> sequence(List<Rand<A>> fs) {
return fs.foldRight(unit(List.list()), f -> acc -> map2(f, acc, x -> y -> y.cons(x)));
}
/*
* A tail-recursive stack safe solution. Note that the output list is in
* reverse order, but this is perfectly acceptable regarding the requirements.
*/
public static Tuple<List<Double>, RNG> doubles(int count, RNG rng) {
return doubles(count, rng, List.list()).eval();
}
public static <A> List<A> toList(Heap<A> heap) {
return heap.tail()
.flatMap(tail -> heap.head().map(head -> toList(tail).cons(head)))
.getOrElse(List.list());
}
public List<A> toList() {
return toList(List.list(), this).eval();
}
/**
* Constructs a non empty list from the given elements.
*
* @param head The first in the non-empty list.
* @param tail The elements to construct a list's tail with.
* @return A non-empty list with the given elements.
*/
@SafeVarargs
public static <A> NonEmptyList<A> nel(final A head, final A... tail) {
return nel(head, List.list(tail));
}
