@Test
public void shouldConvertToStream() {
final Value<Integer> value = of(1, 2, 3);
final Stream<Integer> stream = value.toStream();
if (value.isSingleValued()) {
assertThat(stream).isEqualTo(Stream.of(1));
} else {
assertThat(stream).isEqualTo(Stream.of(1, 2, 3));
}
}
/**
* Randomly chooses one of the given generators.
*
* @param generators A non-empty Iterable of generators
* @param <T> Type to be generated
* @return A new T generator
* @throws java.lang.NullPointerException if generators is null
* @throws java.lang.IllegalArgumentException if generators is empty
*/
static <T> Gen<T> oneOf(Iterable<Gen<T>> generators) {
Objects.requireNonNull(generators, "generators is null");
final Stream<Gen<T>> stream = Stream.ofAll(generators);
if (stream.isEmpty()) {
throw new IllegalArgumentException("generators is empty");
}
@SuppressWarnings("unchecked")
final Gen<T>[] array = stream.toJavaArray((Class<Gen<T>>) (Class) Gen.class);
return oneOf(array);
}
/**
* Chooses one of the given generators according to their frequency.
*
* @param generators A non-empty array of Tuples (frequency, generator)
* @param <T> Type to be generated
* @return A new T generator
* @throws java.lang.NullPointerException if generators is null
* @throws java.lang.IllegalArgumentException if generators is empty
*/
@SafeVarargs
@SuppressWarnings("varargs")
static <T> Gen<T> frequency(Tuple2<Integer, Gen<T>>... generators) {
Objects.requireNonNull(generators, "generators is null");
if (generators.length == 0) {
throw new IllegalArgumentException("generators is empty");
}
final Iterable<Tuple2<Integer, Gen<T>>> iterable = Stream.of(generators);
return frequency(iterable);
}
/**
* Chooses one of the given generators according to their frequency.
*
* @param generators A non-empty traversable of Tuples (frequency, generator)
* @param <T> Type to be generated
* @return A new T generator
* @throws java.lang.NullPointerException if generators is null
* @throws java.lang.IllegalArgumentException if generators is empty
*/
static <T> Gen<T> frequency(Iterable<Tuple2<Integer, Gen<T>>> generators) {
Objects.requireNonNull(generators, "generators is null");
final Stream<Tuple2<Integer, Gen<T>>> stream = Stream.ofAll(generators);
if (stream.isEmpty()) {
throw new IllegalArgumentException("generators is empty");
}
final class Frequency {
Gen<T> gen(int n, Stream<Tuple2<Integer, Gen<T>>> stream) {
final int k = stream.head()._1;
if (k < 0) {
throw new IllegalArgumentException("negative frequency: " + k);
}
return (n <= k) ? stream.head()._2 : gen(n - k, stream.tail());
}
}
final int size = stream.map(t -> t._1).sum().intValue();
return choose(1, size).flatMap(n -> new Frequency().gen(n, stream));
}
private static long sumOfSquaresFrom1UpTo(int max) {
return Stream.rangeClosed(1, max).map(i -> (long) Math.pow(i, 2)).sum().longValue();
}
private static long squareOfSumFrom1UpTo(int max) {
return (long) Math.pow(Stream.rangeClosed(1, max).sum().longValue(), 2);
}
static <T> Gen<T> of(T seed, Function<? super T, ? extends T> next) {
final Iterator<T> iterator = Stream.gen(seed, next).iterator();
return ignored -> iterator.next();
}
public static Stream<Long> primeFactors(long num) {
return Stream.rangeClosed(2L, (int) Math.sqrt(num))
.findFirst(d -> num % d == 0)
.map(d -> Stream.cons(d, () -> primeFactors(num / d)))
.orElseGet(() -> Stream.of(num));
}
public static Stream<Integer> primes() {
return Stream.ofAll(PRIMES_2_000_000);
}