/* / \____ _ _ ____ ______ / \ ____ __ _______
* / / \/ \ / \/ \ / /\__\/ // \/ \ // /\__\ JΛVΛSLΛNG
* _/ / /\ \ \/ / /\ \\__\\ \ // /\ \ /\\/ \ /__\ \ Copyright 2014-2016 Javaslang, http://javaslang.io
* /___/\_/ \_/\____/\_/ \_/\__\/__/\__\_/ \_// \__/\_____/ Licensed under the Apache License, Version 2.0
*/
package javaslang.collection;
import javaslang.Tuple;
import javaslang.Tuple2;
import javaslang.Tuple3;
import javaslang.collection.IteratorModule.ConcatIterator;
import javaslang.collection.IteratorModule.DistinctIterator;
import javaslang.control.Option;
import java.util.Comparator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;
/**
* {@code javaslang.collection.Iterator} is a compositional replacement for {@code java.util.Iterator}
* whose purpose is to iterate once over a sequence of elements.
*
* It is recommended to create instances using {@link AbstractIterator} in favor of {@code Iterator}.
*
* Note: Iterators encapsulate mutable state.
* They are not meant to be used concurrently by different threads. Do not reuse Iterators, e.g. after passing to
* {@linkplain List#ofAll(Iterable)}.
*
* There are two abstract methods: {@code hasNext} for checking if there is a next element available,
* and {@code next} which removes the next element from the iterator and returns it. They can be called
* an arbitrary amount of times. If {@code hasNext} returns false, a call of {@code next} will throw
* a {@code NoSuchElementException}.
*
* Caution: Other methods than {@code hasNext} and {@code next} can be called only once (exclusively).
* More specifically, after calling a method it cannot be guaranteed that the next call will succeed.
*
* An Iterator that can be only used once because it is a traversal pointer into a collection, and not a collection
* itself.
*
* @param Component type
* @author Daniel Dietrich
* @since 2.0.0
*/
public interface Iterator extends java.util.Iterator, Traversable {
// DEV-NOTE: we prefer returning empty() over this if !hasNext() == true in order to free memory.
/**
* The empty Iterator.
*/
Iterator EMPTY = new AbstractIterator() {
@Override
public boolean hasNext() {
return false;
}
@Override
public Object getNext() {
return null;
}
};
/**
* Creates an Iterator which traverses along the concatenation of the given iterables.
*
* @param iterables The iterables
* @param Component type.
* @return A new {@code javaslang.collection.Iterator}
*/
@SuppressWarnings("varargs")
@SafeVarargs
static Iterator concat(Iterable... iterables) {
Objects.requireNonNull(iterables, "iterables is null");
if (iterables.length == 0) {
return empty();
} else {
return new ConcatIterator<>(Stream.of(iterables).map(Iterator::ofAll).iterator());
}
}
/**
* Creates an Iterator which traverses along the concatenation of the given iterables.
*
* @param iterables The iterable of iterables
* @param Component type.
* @return A new {@code javaslang.collection.Iterator}
*/
static Iterator concat(Iterable> iterables) {
Objects.requireNonNull(iterables, "iterables is null");
if (!iterables.iterator().hasNext()) {
return empty();
} else {
return new ConcatIterator<>(Stream.ofAll(iterables).map(Iterator::ofAll).iterator());
}
}
/**
* Returns the empty Iterator.
*
* @param Component type
* @return The empty Iterator
*/
@SuppressWarnings("unchecked")
static Iterator empty() {
return (Iterator) EMPTY;
}
/**
* Narrows a widened {@code Iterator} to {@code Iterator}
* by performing a type safe-cast. This is eligible because immutable/read-only
* collections are covariant.
*
* @param iterator An {@code Iterator}.
* @param Component type of the {@code Iterator}.
* @return the given {@code iterator} instance as narrowed type {@code Iterator}.
*/
@SuppressWarnings("unchecked")
static Iterator narrow(Iterator iterator) {
return (Iterator) iterator;
}
/**
* Creates an Iterator which traverses one element.
*
* @param element An element
* @param Component type.
* @return A new Iterator
*/
static Iterator of(T element) {
return new AbstractIterator() {
boolean hasNext = true;
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public T getNext() {
hasNext = false;
return element;
}
};
}
/**
* Creates an Iterator which traverses the given elements.
*
* @param elements Zero or more elements
* @param Component type
* @return A new Iterator
*/
@SafeVarargs
static Iterator of(T... elements) {
Objects.requireNonNull(elements, "elements is null");
if (elements.length == 0) {
return Iterator.empty();
} else {
return new AbstractIterator() {
int index = 0;
@Override
public boolean hasNext() {
return index < elements.length;
}
@Override
public T getNext() {
return elements[index++];
}
};
}
}
/**
* Creates an Iterator based on the given Iterable. This is a convenience method for
* {@code Iterator.of(iterable.iterator()}.
*
* @param iterable A {@link Iterable}
* @param Component type.
* @return A new {@code javaslang.collection.Iterator}
*/
@SuppressWarnings("unchecked")
static Iterator ofAll(Iterable iterable) {
Objects.requireNonNull(iterable, "iterable is null");
if (iterable instanceof Iterator) {
return (Iterator) iterable;
} else {
return Iterator.ofAll(iterable.iterator());
}
}
/**
* Creates an Iterator based on the given Iterator by
* delegating calls of {@code hasNext()} and {@code next()} to it.
*
* @param iterator A {@link java.util.Iterator}
* @param Component type.
* @return A new {@code javaslang.collection.Iterator}
*/
@SuppressWarnings("unchecked")
static Iterator ofAll(java.util.Iterator iterator) {
Objects.requireNonNull(iterator, "iterator is null");
if (iterator instanceof Iterator) {
return (Iterator) iterator;
} else {
return new AbstractIterator() {
@Override
public boolean hasNext() {
return iterator.hasNext();
}
@Override
public T getNext() {
return iterator.next();
}
};
}
}
/**
* Creates an Iterator based on the elements of a boolean array.
*
* @param array a boolean array
* @return A new Iterator of Boolean values
*/
static Iterator ofAll(boolean[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Boolean getNext() {
return array[i++];
}
};
}
/**
* Creates an Iterator based on the elements of a byte array.
*
* @param array a byte array
* @return A new Iterator of Byte values
*/
static Iterator ofAll(byte[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Byte getNext() {
return array[i++];
}
};
}
/**
* Creates an Iterator based on the elements of a char array.
*
* @param array a char array
* @return A new Iterator of Character values
*/
static Iterator ofAll(char[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Character getNext() {
return array[i++];
}
};
}
/**
* Creates ann Iterator based on the elements of a double array.
*
* @param array a double array
* @return A new Iterator of Double values
*/
static Iterator ofAll(double[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Double getNext() {
return array[i++];
}
};
}
/**
* Creates an Iterator based on the elements of a float array.
*
* @param array a float array
* @return A new Iterator of Float values
*/
static Iterator ofAll(float[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Float getNext() {
return array[i++];
}
};
}
/**
* Creates an Iterator based on the elements of an int array.
*
* @param array an int array
* @return A new Iterator of Integer values
*/
static Iterator ofAll(int[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Integer getNext() {
return array[i++];
}
};
}
/**
* Creates an Iterator based on the elements of a long array.
*
* @param array a long array
* @return A new Iterator of Long values
*/
static Iterator ofAll(long[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Long getNext() {
return array[i++];
}
};
}
/**
* Creates an Iterator based on the elements of a short array.
*
* @param array a short array
* @return A new Iterator of Short values
*/
static Iterator ofAll(short[] array) {
Objects.requireNonNull(array, "array is null");
return new AbstractIterator() {
int i = 0;
@Override
public boolean hasNext() {
return i < array.length;
}
@Override
public Short getNext() {
return array[i++];
}
};
}
/**
* Returns an Iterator on a sequence of {@code n} values of a given Function {@code f}
* over a range of integer values from 0 to {@code n - 1}.
*
* @param Component type of the Iterator
* @param n The number of elements
* @param f The Function computing element values
* @return An Iterator on a sequence of elements {@code f(0),f(1), ..., f(n - 1)}
* @throws NullPointerException if {@code f} is null
*/
static Iterator tabulate(int n, Function f) {
Objects.requireNonNull(f, "f is null");
return Collections.tabulate(n, f);
}
/**
* Returns an Iterator on a sequence of {@code n} values supplied by a given Supplier {@code s}.
*
* @param Component type of the Iterator
* @param n The number of elements
* @param s The Supplier computing element values
* @return An iterator on a sequence of {@code n} elements, where each element contains the result supplied by {@code s}.
* @throws NullPointerException if {@code s} is null
*/
static Iterator fill(int n, Supplier s) {
Objects.requireNonNull(s, "s is null");
return Collections.fill(n, s);
}
/**
* Creates an Iterator of characters starting from {@code from}, extending to {@code toExclusive - 1}.
*
* Examples:
*
*
* Iterator.range('a', 'c') // = ('a', 'b')
* Iterator.range('c', 'a') // = ()
*
*
*
* @param from the first character
* @param toExclusive the successor of the last character
* @return a range of characters as specified or the empty range if {@code from >= toExclusive}
*/
static Iterator range(char from, char toExclusive) {
return Iterator.rangeBy(from, toExclusive, 1);
}
/**
* Creates an Iterator of characters starting from {@code from}, extending to {@code toExclusive - 1},
* with {@code step}.
*
* Examples:
*
*
* Iterator.rangeBy('a', 'c', 1) // = ('a', 'b')
* Iterator.rangeBy('a', 'd', 2) // = ('a', 'c')
* Iterator.rangeBy('d', 'a', -2) // = ('d', 'b')
* Iterator.rangeBy('d', 'a', 2) // = ()
*
*
*
* @param from the first character
* @param toExclusive the successor of the last character if step > 0, the predecessor of the last character if step < 0
* @param step the step
* @return a range of characters as specified or the empty range if {@code (from == toExclusive) || (step * (from - toExclusive) > 0)}.
* @throws IllegalArgumentException if {@code step} is zero
*/
static Iterator rangeBy(char from, char toExclusive, int step) {
return Iterator.rangeBy((int) from, (int) toExclusive, step).map(i -> (char) i.shortValue());
}
static Iterator rangeBy(double from, double toExclusive, double step) {
if (Double.isNaN(from)) {
throw new IllegalArgumentException("from is NaN");
} else if (Double.isNaN(toExclusive)) {
throw new IllegalArgumentException("toExclusive is NaN");
} else if (Double.isNaN(step)) {
throw new IllegalArgumentException("step is NaN");
} else if (step == 0) {
throw new IllegalArgumentException("step cannot be 0");
} else if (step * (from - toExclusive) >= 0) {
return Iterator.empty();
} else {
return new AbstractIterator() {
double prev = Double.NaN;
double curr = from;
boolean hasNext = true;
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public Double getNext() {
final double next = curr;
if ((step > 0 && curr + step >= toExclusive) || (step < 0 && curr + step <= toExclusive)) {
hasNext = false;
} else {
prev = curr;
curr += step;
if (curr == prev) {
hasNext = false;
}
}
return next;
}
};
}
}
/**
* Creates an Iterator of int numbers starting from {@code from}, extending to {@code toExclusive - 1}.
*
* Examples:
*
*
* Iterator.range(0, 0) // = ()
* Iterator.range(2, 0) // = ()
* Iterator.range(-2, 2) // = (-2, -1, 0, 1)
*
*
*
* @param from the first number
* @param toExclusive the last number + 1
* @return a range of int values as specified or the empty range if {@code from >= toExclusive}
*/
static Iterator range(int from, int toExclusive) {
return Iterator.rangeBy(from, toExclusive, 1);
}
/**
* Creates an Iterator of int numbers starting from {@code from}, extending to {@code toExclusive - 1},
* with {@code step}.
*
* Examples:
*
*
* Iterator.rangeBy(1, 3, 1) // = (1, 2)
* Iterator.rangeBy(1, 4, 2) // = (1, 3)
* Iterator.rangeBy(4, 1, -2) // = (4, 2)
* Iterator.rangeBy(4, 1, 2) // = ()
*
*
*
* @param from the first number
* @param toExclusive the last number + 1 if step > 0, the last number - 1 if step < 0
* @param step the step
* @return a range of long values as specified or the empty range if {@code (from == toExclusive) || (step * (from - toExclusive) > 0)}.
* @throws IllegalArgumentException if {@code step} is zero
*/
static Iterator rangeBy(int from, int toExclusive, int step) {
final int one = step > 0 ? 1 : -1;
return Iterator.rangeClosedBy(from, toExclusive - one, step);
}
/**
* Creates an Iterator of long numbers starting from {@code from}, extending to {@code toExclusive - 1}.
*
* Examples:
*
*
* Iterator.range(0L, 0L) // = ()
* Iterator.range(2L, 0L) // = ()
* Iterator.range(-2L, 2L) // = (-2L, -1L, 0L, 1L)
*
*
*
* @param from the first number
* @param toExclusive the last number + 1
* @return a range of long values as specified or the empty range if {@code from >= toExclusive}
*/
static Iterator range(long from, long toExclusive) {
return Iterator.rangeBy(from, toExclusive, 1);
}
/**
* Creates an Iterator of long numbers starting from {@code from}, extending to {@code toExclusive - 1},
* with {@code step}.
*
* Examples:
*
*
* Iterator.rangeBy(1L, 3L, 1L) // = (1L, 2L)
* Iterator.rangeBy(1L, 4L, 2L) // = (1L, 3L)
* Iterator.rangeBy(4L, 1L, -2L) // = (4L, 2L)
* Iterator.rangeBy(4L, 1L, 2L) // = ()
*
*
*
* @param from the first number
* @param toExclusive the last number + 1 if step > 0, the last number - 1 if step < 0
* @param step the step
* @return a range of long values as specified or the empty range if {@code (from == toExclusive) || (step * (from - toExclusive) > 0)}.
* @throws IllegalArgumentException if {@code step} is zero
*/
static Iterator rangeBy(long from, long toExclusive, long step) {
final int one = step > 0 ? 1 : -1;
return Iterator.rangeClosedBy(from, toExclusive - one, step);
}
/**
* Creates an Iterator of characters starting from {@code from}, extending to {@code toInclusive}.
*
* Examples:
*
*
* Iterator.rangeClosed('a', 'c') // = ('a', 'b', 'c')
* Iterator.rangeClosed('c', 'a') // = ()
*
*
*
* @param from the first character
* @param toInclusive the last character
* @return a range of characters as specified or the empty range if {@code from > toInclusive}
*/
static Iterator rangeClosed(char from, char toInclusive) {
return Iterator.rangeClosedBy(from, toInclusive, 1);
}
/**
* Creates an Iterator of characters starting from {@code from}, extending to {@code toInclusive},
* with {@code step}.
*
* Examples:
*
*
* Iterator.rangeClosedBy('a', 'c', 1) // = ('a', 'b', 'c')
* Iterator.rangeClosedBy('a', 'd', 2) // = ('a', 'c')
* Iterator.rangeClosedBy('d', 'a', -2) // = ('d', 'b')
* Iterator.rangeClosedBy('d', 'a', 2) // = ()
*
*
*
* @param from the first character
* @param toInclusive the last character
* @param step the step
* @return a range of characters as specified or the empty range if {@code step * (from - toInclusive) > 0}.
* @throws IllegalArgumentException if {@code step} is zero
*/
static Iterator rangeClosedBy(char from, char toInclusive, int step) {
return Iterator.rangeClosedBy((int) from, (int) toInclusive, step).map(i -> (char) i.shortValue());
}
static Iterator rangeClosedBy(double from, double toInclusive, double step) {
if (Double.isNaN(from)) {
throw new IllegalArgumentException("from is NaN");
} else if (Double.isNaN(toInclusive)) {
throw new IllegalArgumentException("toInclusive is NaN");
} else if (Double.isNaN(step)) {
throw new IllegalArgumentException("step is NaN");
} else if (step == 0) {
throw new IllegalArgumentException("step cannot be 0");
} else if (from == toInclusive) {
return Iterator.of(from);
} else if (step * (from - toInclusive) > 0) {
return Iterator.empty();
} else {
return new AbstractIterator() {
double prev = Double.NaN;
double curr = from;
boolean hasNext = true;
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public Double getNext() {
final double next = curr;
if ((step > 0 && curr + step > toInclusive) || (step < 0 && curr + step < toInclusive)) {
hasNext = false;
} else {
prev = curr;
curr += step;
if (curr == prev) {
hasNext = false;
}
}
return next;
}
};
}
}
/**
* Creates an Iterator of int numbers starting from {@code from}, extending to {@code toInclusive}.
*
* Examples:
*
*
* Iterator.rangeClosed(0, 0) // = (0)
* Iterator.rangeClosed(2, 0) // = ()
* Iterator.rangeClosed(-2, 2) // = (-2, -1, 0, 1, 2)
*
*
*
* @param from the first number
* @param toInclusive the last number
* @return a range of int values as specified or the empty range if {@code from > toInclusive}
*/
static Iterator rangeClosed(int from, int toInclusive) {
return Iterator.rangeClosedBy(from, toInclusive, 1);
}
/**
* Creates an Iterator of int numbers starting from {@code from}, extending to {@code toInclusive},
* with {@code step}.
*
* Examples:
*
*
* Iterator.rangeClosedBy(1, 3, 1) // = (1, 2, 3)
* Iterator.rangeClosedBy(1, 4, 2) // = (1, 3)
* Iterator.rangeClosedBy(4, 1, -2) // = (4, 2)
* Iterator.rangeClosedBy(4, 1, 2) // = ()
*
*
*
* @param from the first number
* @param toInclusive the last number
* @param step the step
* @return a range of int values as specified or the empty range if {@code step * (from - toInclusive) > 0}.
* @throws IllegalArgumentException if {@code step} is zero
*/
static Iterator rangeClosedBy(int from, int toInclusive, int step) {
if (step == 0) {
throw new IllegalArgumentException("step cannot be 0");
} else if (from == toInclusive) {
return Iterator.of(from);
} else if (Integer.signum(step) * Integer.signum(from - toInclusive) > 0) {
return Iterator.empty();
} else {
return new AbstractIterator() {
int i = from;
boolean hasNext = true;
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public Integer getNext() {
final int next = i;
if ((step > 0 && i > toInclusive - step) || (step < 0 && i < toInclusive - step)) {
hasNext = false;
} else {
i += step;
}
return next;
}
};
}
}
/**
* Creates an Iterator of long numbers starting from {@code from}, extending to {@code toInclusive}.
*
* Examples:
*
*
* Iterator.rangeClosed(0L, 0L) // = (0L)
* Iterator.rangeClosed(2L, 0L) // = ()
* Iterator.rangeClosed(-2L, 2L) // = (-2L, -1L, 0L, 1L, 2L)
*
*
*
* @param from the first number
* @param toInclusive the last number
* @return a range of long values as specified or the empty range if {@code from > toInclusive}
*/
static Iterator rangeClosed(long from, long toInclusive) {
return Iterator.rangeClosedBy(from, toInclusive, 1L);
}
/**
* Creates an Iterator of long numbers starting from {@code from}, extending to {@code toInclusive},
* with {@code step}.
*
* Examples:
*
*
* Iterator.rangeClosedBy(1L, 3L, 1L) // = (1L, 2L, 3L)
* Iterator.rangeClosedBy(1L, 4L, 2L) // = (1L, 3L)
* Iterator.rangeClosedBy(4L, 1L, -2L) // = (4L, 2L)
* Iterator.rangeClosedBy(4L, 1L, 2L) // = ()
*
*
*
* @param from the first number
* @param toInclusive the last number
* @param step the step
* @return a range of int values as specified or the empty range if {@code step * (from - toInclusive) > 0}.
* @throws IllegalArgumentException if {@code step} is zero
*/
static Iterator rangeClosedBy(long from, long toInclusive, long step) {
if (step == 0L) {
throw new IllegalArgumentException("step cannot be 0");
} else if (from == toInclusive) {
return Iterator.of(from);
} else if (Long.signum(step) * Long.signum(from - toInclusive) > 0L) {
return Iterator.empty();
} else {
return new AbstractIterator() {
long i = from;
boolean hasNext = true;
@Override
public boolean hasNext() {
return hasNext;
}
@Override
public Long getNext() {
final long next = i;
if ((step > 0L && i > toInclusive - step) || (step < 0L && i < toInclusive - step)) {
hasNext = false;
} else {
i += step;
}
return next;
}
};
}
}
/**
* Returns an infinite iterator of int values starting from {@code value}.
*
* The {@code Iterator} extends to {@code Integer.MIN_VALUE} when passing {@code Integer.MAX_VALUE}.
*
* @param value a start int value
* @return a new {@code Iterator} of int values starting from {@code from}
*/
static Iterator from(int value) {
return new AbstractIterator() {
private int next = value;
@Override
public boolean hasNext() {
return true;
}
@Override
public Integer getNext() {
return next++;
}
};
}
/**
* Returns an infinite iterator of int values starting from {@code value} and spaced by {@code step}.
*
* The {@code Iterator} extends to {@code Integer.MIN_VALUE} when passing {@code Integer.MAX_VALUE}.
*
* @param value a start int value
* @param step the step by which to advance on each iteration
* @return a new {@code Iterator} of int values starting from {@code from}
*/
static Iterator from(int value, int step) {
return new AbstractIterator() {
private int next = value;
@Override
public boolean hasNext() {
return true;
}
@Override
public Integer getNext() {
int result = next;
next += step;
return result;
}
};
}
/**
* Returns an infinite iterator of long values starting from {@code value}.
*
* The {@code Iterator} extends to {@code Long.MIN_VALUE} when passing {@code Long.MAX_VALUE}.
*
* @param value a start long value
* @return a new {@code Iterator} of long values starting from {@code from}
*/
static Iterator from(long value) {
return new AbstractIterator() {
private long next = value;
@Override
public boolean hasNext() {
return true;
}
@Override
public Long getNext() {
return next++;
}
};
}
/**
* Returns an infinite iterator of long values starting from {@code value} and spaced by {@code step}.
*
* The {@code Iterator} extends to {@code Long.MIN_VALUE} when passing {@code Long.MAX_VALUE}.
*
* @param value a start long value
* @param step the step by which to advance on each iteration
* @return a new {@code Iterator} of long values starting from {@code from}
*/
static Iterator from(long value, long step) {
return new AbstractIterator() {
private long next = value;
@Override
public boolean hasNext() {
return true;
}
@Override
public Long getNext() {
long result = next;
next += step;
return result;
}
};
}
/**
* Generates an infinite iterator using a value Supplier.
*
* @param supplier A Supplier of iterator values
* @param value type
* @return A new {@code Iterator}
*/
static Iterator continually(Supplier supplier) {
Objects.requireNonNull(supplier, "supplier is null");
return new AbstractIterator() {
@Override
public boolean hasNext() {
return true;
}
@Override
public T getNext() {
return supplier.get();
}
};
}
/**
* Generates an infinite iterator using a function to calculate the next value
* based on the previous.
*
* @param seed The first value in the iterator
* @param f A function to calculate the next value based on the previous
* @param value type
* @return A new {@code Iterator}
*/
static Iterator iterate(T seed, Function f) {
Objects.requireNonNull(f, "f is null");
return new AbstractIterator() {
Function nextFunc = s -> {
nextFunc = f;
return seed;
};
T current = null;
@Override
public boolean hasNext() {
return true;
}
@Override
public T getNext() {
current = nextFunc.apply(current);
return current;
}
};
}
/**
* Creates an infinite iterator returning the given element.
*
* @param t An element
* @param Element type
* @return A new Iterator containing infinite {@code t}'s.
*/
static Iterator continually(T t) {
return new AbstractIterator() {
@Override
public boolean hasNext() {
return true;
}
@Override
public T getNext() {
return t;
}
};
}
// -- Additional methods of Iterator
// DEV-NOTE: cannot use arg Iterable, it would be ambiguous
default Iterator concat(java.util.Iterator that) {
Objects.requireNonNull(that, "that is null");
if (!that.hasNext()) {
return this;
} else if (!hasNext()) {
return Iterator.ofAll(that);
} else {
return Iterator.concat(this, Iterator.ofAll(that));
}
}
/**
* Inserts an element between all elements of this Iterator.
*
* @param element An element.
* @return an interspersed version of this
*/
default Iterator intersperse(T element) {
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
boolean insertElement = false;
@Override
public boolean hasNext() {
return that.hasNext();
}
@Override
public T getNext() {
if (insertElement) {
insertElement = false;
return element;
} else {
insertElement = true;
return that.next();
}
}
};
}
}
/**
* Transforms this {@code Iterator}.
*
* @param f A transformation
* @param Type of transformation result
* @return An instance of type {@code U}
* @throws NullPointerException if {@code f} is null
*/
default U transform(Function, ? extends U> f) {
Objects.requireNonNull(f, "f is null");
return f.apply(this);
}
@Override
default Iterator> zip(Iterable that) {
Objects.requireNonNull(that, "that is null");
if (isEmpty()) {
return empty();
} else {
final Iterator it1 = this;
final java.util.Iterator it2 = that.iterator();
return new AbstractIterator>() {
@Override
public boolean hasNext() {
return it1.hasNext() && it2.hasNext();
}
@Override
public Tuple2 getNext() {
return Tuple.of(it1.next(), it2.next());
}
};
}
}
@Override
default Iterator> zipAll(Iterable that, T thisElem, U thatElem) {
Objects.requireNonNull(that, "that is null");
final java.util.Iterator thatIt = that.iterator();
if (isEmpty() && !thatIt.hasNext()) {
return empty();
} else {
final Iterator thisIt = this;
return new AbstractIterator>() {
@Override
public boolean hasNext() {
return thisIt.hasNext() || thatIt.hasNext();
}
@Override
public Tuple2 getNext() {
T v1 = thisIt.hasNext() ? thisIt.next() : thisElem;
U v2 = thatIt.hasNext() ? thatIt.next() : thatElem;
return Tuple.of(v1, v2);
}
};
}
}
@Override
default Iterator> zipWithIndex() {
if (isEmpty()) {
return empty();
} else {
final Iterator it1 = this;
return new AbstractIterator>() {
private long index = 0;
@Override
public boolean hasNext() {
return it1.hasNext();
}
@Override
public Tuple2 getNext() {
return Tuple.of(it1.next(), index++);
}
};
}
}
@Override
default Tuple2, Iterator> unzip(
Function> unzipper) {
Objects.requireNonNull(unzipper, "unzipper is null");
if (!hasNext()) {
return Tuple.of(empty(), empty());
} else {
final Stream> source = Stream.ofAll(this.map(unzipper));
return Tuple.of(source.map(t -> (T1) t._1).iterator(), source.map(t -> (T2) t._2).iterator());
}
}
@Override
default Tuple3, Iterator, Iterator> unzip3(
Function> unzipper) {
Objects.requireNonNull(unzipper, "unzipper is null");
if (!hasNext()) {
return Tuple.of(empty(), empty(), empty());
} else {
final Stream> source = Stream.ofAll(this.map(unzipper));
return Tuple.of(source.map(t -> (T1) t._1).iterator(), source.map(t -> (T2) t._2).iterator(), source.map(t -> (T3) t._3).iterator());
}
}
// -- Overridden methods of Traversable
@Override
default Iterator distinct() {
if (!hasNext()) {
return empty();
} else {
return new DistinctIterator<>(this, HashSet.empty(), Function.identity());
}
}
@Override
default Iterator distinctBy(Comparator comparator) {
Objects.requireNonNull(comparator, "comparator is null");
if (!hasNext()) {
return empty();
} else {
return new DistinctIterator<>(this, TreeSet.empty(comparator), Function.identity());
}
}
@Override
default Iterator distinctBy(Function keyExtractor) {
Objects.requireNonNull(keyExtractor, "keyExtractor is null");
if (!hasNext()) {
return empty();
} else {
return new DistinctIterator<>(this, HashSet.empty(), keyExtractor);
}
}
/**
* Removes up to n elements from this iterator.
*
* @param n A number
* @return The empty iterator, if {@code n <= 0} or this is empty, otherwise a new iterator without the first n elements.
*/
@Override
default Iterator drop(long n) {
if (n <= 0) {
return this;
} else if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
long count = n;
@Override
public boolean hasNext() {
while (count > 0 && that.hasNext()) {
that.next(); // discarded
count--;
}
return that.hasNext();
}
@Override
public T getNext() {
return that.next();
}
};
}
}
@Override
default Iterator dropRight(long n) {
if (n <= 0) {
return this;
} else if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
private Queue queue = Queue.empty();
@Override
public boolean hasNext() {
while (queue.length() < n && that.hasNext()) {
queue = queue.append(that.next());
}
return queue.length() == n && that.hasNext();
}
@Override
public T getNext() {
Tuple2> t = queue.append(that.next()).dequeue();
queue = t._2;
return t._1;
}
};
}
}
@Override
default Iterator dropUntil(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
return dropWhile(predicate.negate());
}
@Override
default Iterator dropWhile(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
private T next = null;
@Override
public boolean hasNext() {
while (next == null && that.hasNext()) {
final T value = that.next();
if (!predicate.test(value)) {
next = value;
}
}
return next != null;
}
@Override
public T getNext() {
final T result = next;
next = null;
return result;
}
};
}
}
/**
* Returns an Iterator that contains elements that satisfy the given {@code predicate}.
*
* @param predicate A predicate
* @return A new Iterator
*/
@Override
default Iterator filter(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
Option next = Option.none();
@Override
public boolean hasNext() {
while (next.isEmpty() && that.hasNext()) {
final T candidate = that.next();
if (predicate.test(candidate)) {
next = Option.some(candidate);
}
}
return next.isDefined();
}
@Override
public T getNext() {
T result = next.get();
next = Option.none();
return result;
}
};
}
}
@Override
default Option findLast(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
T last = null;
while (hasNext()) {
final T elem = next();
if (predicate.test(elem)) {
last = elem;
}
}
return Option.of(last);
}
/**
* FlatMaps the elements of this Iterator to Iterables, which are iterated in the order of occurrence.
*
* @param mapper A mapper
* @param Component type
* @return A new Iterable
*/
@Override
default Iterator flatMap(Function> mapper) {
Objects.requireNonNull(mapper, "mapper is null");
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
final Iterator inputs = that;
java.util.Iterator current = java.util.Collections.emptyIterator();
@Override
public boolean hasNext() {
boolean currentHasNext;
while (!(currentHasNext = current.hasNext()) && inputs.hasNext()) {
current = mapper.apply(inputs.next()).iterator();
}
return currentHasNext;
}
@Override
public U getNext() {
return current.next();
}
};
}
}
@Override
default U foldRight(U zero, BiFunction f) {
Objects.requireNonNull(f, "f is null");
return Stream.ofAll(this).foldRight(zero, f);
}
@Override
default T get() {
return head();
}
@Override
default Map> groupBy(Function classifier) {
return Collections.groupBy(this, classifier, Iterator::ofAll);
}
@Override
default Iterator> grouped(long size) {
return sliding(size, size);
}
@Override
default boolean hasDefiniteSize() {
return false;
}
@Override
default T head() {
if (!hasNext()) {
throw new NoSuchElementException("head() on empty iterator");
}
return next();
}
@Override
default Option headOption() {
return hasNext() ? Option.some(next()) : Option.none();
}
@Override
default Iterator init() {
if (!hasNext()) {
throw new UnsupportedOperationException();
} else {
return dropRight(1);
}
}
@Override
default Option> initOption() {
return hasNext() ? Option.some(init()) : Option.none();
}
@Override
default boolean isEmpty() {
return !hasNext();
}
@Override
default boolean isTraversableAgain() {
return false;
}
@Override
default Iterator iterator() {
return this;
}
@Override
default int length() {
return foldLeft(0, (n, ignored) -> n + 1);
}
/**
* Maps the elements of this Iterator lazily using the given {@code mapper}.
*
* @param mapper A mapper.
* @param Component type
* @return A new Iterator
*/
@Override
default Iterator map(Function mapper) {
Objects.requireNonNull(mapper, "mapper is null");
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
@Override
public boolean hasNext() {
return that.hasNext();
}
@Override
public U getNext() {
return mapper.apply(that.next());
}
};
}
}
@Override
default Tuple2, Iterator> partition(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
if (!hasNext()) {
return Tuple.of(empty(), empty());
} else {
final Stream that = Stream.ofAll(this);
final Iterator first = that.iterator().filter(predicate);
final Iterator second = that.iterator().filter(predicate.negate());
return Tuple.of(first, second);
}
}
@Override
default Iterator peek(Consumer action) {
Objects.requireNonNull(action, "action is null");
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
@Override
public boolean hasNext() {
return that.hasNext();
}
@Override
public T getNext() {
final T next = that.next();
action.accept(next);
return next;
}
};
}
}
@Override
default T reduceLeft(BiFunction op) {
Objects.requireNonNull(op, "op is null");
if (isEmpty()) {
throw new NoSuchElementException("reduceLeft on Nil");
} else {
Stream stream = Stream.ofAll(this);
return stream.tail().foldLeft(stream.head(), op);
}
}
@Override
default T reduceRight(BiFunction op) {
Objects.requireNonNull(op, "op is null");
if (isEmpty()) {
throw new NoSuchElementException("reduceRight on Nil");
} else {
Stream reversed = Stream.ofAll(this).reverse();
return reversed.tail().foldLeft(reversed.head(), (xs, x) -> op.apply(x, xs));
}
}
@Override
default Iterator replace(T currentElement, T newElement) {
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
boolean done = false;
@Override
public boolean hasNext() {
return that.hasNext();
}
@Override
public T getNext() {
final T elem = that.next();
if (done || !Objects.equals(currentElement, elem)) {
return elem;
} else {
done = true;
return newElement;
}
}
};
}
}
@Override
default Iterator replaceAll(T currentElement, T newElement) {
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
@Override
public boolean hasNext() {
return that.hasNext();
}
@Override
public T getNext() {
final T elem = that.next();
if (Objects.equals(currentElement, elem)) {
return newElement;
} else {
return elem;
}
}
};
}
}
@SuppressWarnings("unchecked")
@Override
default Iterator retainAll(Iterable elements) {
Objects.requireNonNull(elements, "elements is null");
// DEV-NOTE: Only Eclipse does need this unchecked cast, IntelliJ and javac are fine.
return hasNext() ? filter(HashSet.ofAll((Iterable) elements)::contains) : empty();
}
@Override
default Traversable scan(T zero, BiFunction operation) {
return scanLeft(zero, operation);
}
@Override
default Iterator scanLeft(U zero, BiFunction operation) {
Objects.requireNonNull(operation, "operation is null");
if (isEmpty()) {
return Iterator.of(zero);
} else {
final Iterator that = this;
return new AbstractIterator() {
boolean isFirst = true;
U acc = zero;
@Override
public boolean hasNext() {
return isFirst || that.hasNext();
}
@Override
public U getNext() {
if (isFirst) {
isFirst = false;
return acc;
} else {
acc = operation.apply(acc, that.next());
return acc;
}
}
};
}
}
// not lazy!
@Override
default Iterator scanRight(U zero, BiFunction operation) {
Objects.requireNonNull(operation, "operation is null");
if (isEmpty()) {
return Iterator.of(zero);
} else {
return Collections.scanRight(this, zero, operation, Stream.empty(), Stream::prepend, Stream::iterator);
}
}
@Override
default Iterator> sliding(long size) {
return sliding(size, 1);
}
@Override
default Iterator> sliding(long size, long step) {
if (size <= 0 || step <= 0) {
throw new IllegalArgumentException(String.format("size: %s or step: %s not positive", size, step));
}
if (!hasNext()) {
return empty();
} else {
final Stream source = Stream.ofAll(this);
return new AbstractIterator>() {
private Stream that = source;
private IndexedSeq next = null;
@Override
public boolean hasNext() {
while (next == null && !that.isEmpty()) {
final Tuple2, Stream> split = that.splitAt(size);
next = split._1.toVector();
that = split._2.isEmpty() ? Stream. empty() : that.drop(step);
}
return next != null;
}
@Override
public IndexedSeq getNext() {
final IndexedSeq result = next;
next = null;
return result;
}
};
}
}
@Override
default Tuple2, Iterator> span(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
if (!hasNext()) {
return Tuple.of(empty(), empty());
} else {
Stream that = Stream.ofAll(this);
return Tuple.of(that.iterator().takeWhile(predicate), that.iterator().dropWhile(predicate));
}
}
@Override
default Spliterator spliterator() {
// the focus of the Stream API is on random-access collections of *known size*
Stream stream = Stream.ofAll(this);
return Spliterators.spliterator(stream.iterator(), stream.length(),
Spliterator.ORDERED | Spliterator.IMMUTABLE);
}
@Override
default String stringPrefix() {
return "Iterator";
}
@Override
default Iterator tail() {
if (!hasNext()) {
throw new UnsupportedOperationException();
} else {
next(); // remove first element
return this;
}
}
@Override
default Option> tailOption() {
if (hasNext()) {
next();
return Option.some(this);
} else {
return Option.none();
}
}
/**
* Take the first n elements from this iterator.
*
* @param n A number
* @return The empty iterator, if {@code n <= 0} or this is empty, otherwise a new iterator without the first n elements.
*/
@Override
default Iterator take(long n) {
if (n <= 0 || !hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
long count = n;
@Override
public boolean hasNext() {
return count > 0 && that.hasNext();
}
@Override
public T getNext() {
count--;
return that.next();
}
};
}
}
@Override
default Iterator takeRight(long n) {
if (n <= 0) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
private Queue queue = Queue.empty();
@Override
public boolean hasNext() {
while (that.hasNext()) {
queue = queue.enqueue(that.next());
if (queue.length() > n) {
queue = queue.dequeue()._2;
}
}
return queue.length() > 0;
}
@Override
public T getNext() {
final Tuple2> t = queue.dequeue();
queue = t._2;
return t._1;
}
};
}
}
@Override
default Iterator takeUntil(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
return takeWhile(predicate.negate());
}
@Override
default Iterator takeWhile(Predicate predicate) {
Objects.requireNonNull(predicate, "predicate is null");
if (!hasNext()) {
return empty();
} else {
final Iterator that = this;
return new AbstractIterator() {
private T next = null;
private boolean finished = false;
@Override
public boolean hasNext() {
while (!finished && next == null && that.hasNext()) {
final T value = that.next();
if (predicate.test(value)) {
next = value;
} else {
finished = true;
}
}
return next != null;
}
@Override
public T getNext() {
final T result = next;
next = null;
return result;
}
};
}
}
}
interface IteratorModule {
final class ConcatIterator extends AbstractIterator {
private final Iterator> iterators;
private Iterator current;
ConcatIterator(Iterator> iterators) {
this.current = Iterator.empty();
this.iterators = iterators;
}
@Override
public boolean hasNext() {
while (!current.hasNext() && !iterators.isEmpty()) {
current = iterators.next();
}
return current.hasNext();
}
@Override
public T getNext() {
return current.next();
}
}
final class DistinctIterator extends AbstractIterator {
private final Iterator that;
private Set known;
private final Function keyExtractor;
private T next = null;
DistinctIterator(Iterator that, Set set, Function keyExtractor) {
this.that = that;
this.known = set;
this.keyExtractor = keyExtractor;
}
@Override
public boolean hasNext() {
while (next == null && that.hasNext()) {
final T elem = that.next();
final U key = keyExtractor.apply(elem);
if (!known.contains(key)) {
known = known.add(key);
next = elem;
}
}
return next != null;
}
@Override
public T getNext() {
final T result = next;
next = null;
return result;
}
}
}
