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Library providing immutable/persistent collection classes for
Java. While collections are immutable they provide methods for
adding and removing values by creating new modified copies of
themselves. Each copy shares almost all of its structure with
other copies to minimize memory consumption.
///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
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// Copyright (c) 2017, Burton Computer Corporation
// All rights reserved.
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package org.javimmutable.collections.util;
import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Cursorable;
import org.javimmutable.collections.Func1;
import org.javimmutable.collections.Func2;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.Holders;
import org.javimmutable.collections.Insertable;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.list.JImmutableLinkedStack;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
/**
* Library of static functions that perform various operations on Cursors.
*/
public final class Functions
{
private Functions()
{
}
/**
* Calls func for every value in cursor passing in the accumulator and each value as parameters
* and setting accumulator to the result. The final accumulator value is returned.
*/
public static R foldLeft(R accumulator,
Cursor cursor,
Func2 func)
{
for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
accumulator = func.apply(accumulator, cursor.getValue());
}
return accumulator;
}
/**
* Calls func for every value in cursor from right to left (i.e. in reverse order) passing in the accumulator and each value
* as parameters and setting the accumulator to the result. The final accumulator value is returned.
* Requires 2x time compared to foldLeft() since it reverses the order of the cursor before calling the function.
*/
public static R foldRight(R accumulator,
Cursor cursor,
Func2 func)
{
return foldLeft(accumulator, reverse(cursor), func);
}
/**
* Creates a new Cursor whose values are in the reverse order of the provided Cursor.
* Requires O(n) time and creates an intermediate copy of the Cursor's values.
*/
public static Cursor reverse(Cursor cursor)
{
return JImmutableLinkedStack.of().insertAll(cursor).cursor();
}
/**
* Calls func for every value in cursor and adds each value returned by func
* to a list. Returns the resulting list.
*
* @param cursor source of the values
* @param func function to transform the values
* @param list list to receive the values
*/
@SuppressWarnings("unchecked")
public static > A collectAll(Cursor cursor,
A list,
Func1 func)
{
for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
list = list.insert(func.apply(cursor.getValue()));
}
return list;
}
/**
* Calls func for every value in cursor and adds each value for which func returns a non-empty
* Holder to a list. Returns the resulting list.
*
* @param cursor source of the values
* @param func function to reject the values
* @param list list to receive the values
*/
@SuppressWarnings("unchecked")
public static > A collectSome(Cursor cursor,
A list,
Func1> func)
{
for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
Holder mappedValue = func.apply(cursor.getValue());
if (mappedValue.isFilled()) {
list = list.insert(mappedValue.getValue());
}
}
return list;
}
/**
* Calls func for each value in cursor and passes it to func until func returns true.
* If func returns true the value is returned. If func never returns true an empty
* value is returned.
*/
public static Holder find(Cursor cursor,
Func1 func)
{
for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
if (func.apply(cursor.getValue())) {
return Holders.of(cursor.getValue());
}
}
return Holders.of();
}
/**
* Calls func for every value in cursor and adds each value for which func returns false
* to a list. Returns the resulting list.
*
* @param cursor source of the values
* @param func function to reject the values
* @param list list to receive the values
*/
@SuppressWarnings("unchecked")
public static > A reject(Cursor cursor,
A list,
Func1 func)
{
for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
if (!func.apply(cursor.getValue())) {
list = list.insert(cursor.getValue());
}
}
return list;
}
/**
* Calls func for every value in cursor and adds each value for which func returns true
* to a list. Returns the resulting list.
*
* @param cursor source of the values
* @param func function to select the values
* @param list list to receive the values
*/
@SuppressWarnings("unchecked")
public static > A select(Cursor cursor,
A list,
Func1 func)
{
for (cursor = cursor.start(); cursor.hasValue(); cursor = cursor.next()) {
if (func.apply(cursor.getValue())) {
list = list.insert(cursor.getValue());
}
}
return list;
}
/**
* Add all values form the iterator to the addable.
*/
@Deprecated
public static > A insertAll(A addable,
Iterator iterator)
{
return addable.insertAll(iterator);
}
/**
* Add all values form the cursor to the addable.
*/
@Deprecated
public static > A insertAll(A addable,
Cursor cursor)
{
return addable.insertAll(cursor);
}
/**
* Add all values form the array to the addable.
*/
@Deprecated
public static > A insertAll(A addable,
T[] values)
{
return addable.insertAll(Arrays.asList(values));
}
public static JImmutableMap assignAll(JImmutableMap dest,
JImmutableMap src)
{
for (JImmutableMap.Entry entry : src) {
dest = dest.assign(entry.getKey(), entry.getValue());
}
return dest;
}
public static JImmutableMap assignAll(JImmutableMap dest,
Map src)
{
for (Map.Entry entry : src.entrySet()) {
dest = dest.assign(entry.getKey(), entry.getValue());
}
return dest;
}
/**
* Returns an Iterable that can be used to navigate each element in the specified Cursor.
* The Cursor must not have been started yet. Intended for use in java foreach loops.
*
* @deprecated Cursors are Iterable so this function is not needed
*/
@Deprecated
public static Iterable each(final Cursor cursor)
{
return cursor;
}
/**
* Returns an Iterable that can be used to navigate each element in the specified Cursorable.
* Intended for use in java foreach loops.
*
* @deprecated Cursors are Iterable so just use cursorable.cursor()
*/
@Deprecated
public static Iterable each(final Cursorable cursorable)
{
return cursorable.cursor();
}
}