org.javimmutable.collections.util.Functions Maven / Gradle / Ivy
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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();
}
}
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