org.organicdesign.fp.StaticImports Maven / Gradle / Ivy
// Copyright 2014-09-22 PlanBase Inc. & Glen Peterson
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.organicdesign.fp;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Map;
import org.organicdesign.fp.collections.ImList;
import org.organicdesign.fp.collections.ImMap;
import org.organicdesign.fp.collections.ImSet;
import org.organicdesign.fp.collections.ImSortedMap;
import org.organicdesign.fp.collections.ImSortedSet;
import org.organicdesign.fp.collections.PersistentHashMap;
import org.organicdesign.fp.collections.PersistentHashSet;
import org.organicdesign.fp.collections.PersistentTreeMap;
import org.organicdesign.fp.collections.PersistentTreeSet;
import org.organicdesign.fp.collections.PersistentVector;
import org.organicdesign.fp.tuple.Tuple2;
import org.organicdesign.fp.tuple.Tuple3;
import org.organicdesign.fp.xform.Transformable;
import org.organicdesign.fp.xform.Xform;
/**
A mini data definition language composed of vec(), tup(), map(), set(), plus xform() which makes
java.util collections transformable.
import org.organicdesign.fp.StaticImports.*
// Create a new vector of integers
vec(1, 2, 3, 4);
// Create a new set of Strings
set("a", "b", "c");
// Create a tuple of an int and a string (a type-safe heterogeneous container)
tup("a", 1);
// Create a map with a few key value pairs
map(tup("a", 1), tup("b", 2), tup("c", 3);
vec(), map(), and set() are the only three methods in this project to take varargs. I tried
writing out versions that took multiple type-safe arguments, but IntelliJ presented you with a
menu of all of them for auto-completion which was overwhelming, so I reverted to varargs. Also,
varargs relax some type safety rules (variance) for data definition in a generally helpful (rarely
dangerous) way.
If you're used to Clojure/JSON, you'll find that what's a map (dictionary) in those languages
usually becomes a tuple in Paguro. A true map data structure in a type-safe language is
homogeneous, meaning that every member is of the same type (or a descendant of a common ancestor).
Tuples are designed to contain unrelated data types and enforce those types.
As with any usage of import *, there could be issues if you import 2 different versions of this
file in your classpath. Java needs a data definition language so badly that I think it is worth
the risk. Also, I don't anticipate this file changing much, except to add more tup()
implementations, which shouldn't break anything. Let me know if you find that the danger outweighs
convenience or have advice on what to do about it.
*/
@SuppressWarnings("UnusedDeclaration")
public final class StaticImports {
// Prevent instantiation
private StaticImports() { throw new UnsupportedOperationException("No instantiation"); }
/**
This turned out to be a bad idea due to the complexity and slowness of serializing
a class extended from an immutable tuple. I made tuples serializable and was able to back out
other breaking changes.
*/
@Deprecated
public static Tuple2 kv(K t, V u) { return Tuple2.of(t, u); }
/**
Returns a new PersistentHashMap of the given keys and their paired values. Use the
{@link StaticImports#tup(Object, Object)} method to define those key/value pairs briefly and
easily. This data definition method is one of the three methods in this project that support
varargs.
@param kvPairs Key/value pairs (to go into the map). In the case of a duplicate key, later
values in the input list overwrite the earlier ones. The resulting map can contain zero or one
null key and any number of null values. Null k/v pairs will be silently ignored.
@return a new PersistentHashMap of the given key/value pairs
*/
@SafeVarargs
public static ImMap map(Map.Entry... kvPairs) {
if ( (kvPairs == null) || (kvPairs.length < 1) ) { return PersistentHashMap.empty(); }
return PersistentHashMap.of(Arrays.asList(kvPairs));
}
/**
Returns a new PersistentHashSet of the values. This data definition method is one of the three
methods in this project that support varargs. If the input contains duplicate elements, later
values overwrite earlier ones.
*/
@SafeVarargs
public static ImSet set(T... items) {
if ( (items == null) || (items.length < 1) ) { return PersistentHashSet.empty(); }
return PersistentHashSet.of(Arrays.asList(items));
}
/**
Returns a new PersistentTreeMap of the specified comparator and the given key/value pairs. Use
the tup() method to define those key/value pairs briefly and easily. The keys are sorted
according to the comparator you provide.
@param comp A comparator (on the keys) that defines the sort order inside the new map. This
becomes a permanent part of the map and all sub-maps or appended maps derived from it. If you
want to use a null key, make sure the comparator treats nulls correctly in all circumstances!
@param kvPairs Key/value pairs (to go into the map). In the case of a duplicate key, later
values in the input list overwrite the earlier ones. The resulting map can contain zero or one
null key (if your comparator knows how to sort nulls) and any number of null values. Null k/v
pairs will be silently ignored.
@return a new PersistentTreeMap of the specified comparator and the given key/value pairs
*/
public static ImSortedMap
sortedMap(Comparator comp, Iterable> kvPairs) {
return PersistentTreeMap.ofComp(comp, kvPairs);
}
/**
Returns a new PersistentTreeMap of the given comparable keys and their paired values, sorted in
the default ordering of the keys. Use the tup() method to define those key/value pairs briefly
and easily.
@param kvPairs Key/value pairs (to go into the map). In the case of a duplicate key, later
values overwrite earlier ones.
@return a new PersistentTreeMap of the specified comparator and the given key/value pairs which
uses the default comparator defined on the element type.
*/
public static ,V> ImSortedMap
sortedMap(Iterable> kvPairs) { return PersistentTreeMap.of(kvPairs); }
/**
Returns a new PersistentTreeSet of the given comparator and items.
@param comp A comparator that defines the sort order of elements in the new set. This
becomes part of the set (it's not for pre-sorting).
@param elements items to go into the set. In the case of duplicates, later elements overwrite
earlier ones.
@return a new PersistentTreeSet of the specified comparator and the given elements
*/
public static ImSortedSet sortedSet(Comparator comp, Iterable elements) {
return Xform.of(elements).toImSortedSet(comp);
}
/** Returns a new PersistentTreeSet of the given comparable items. */
public static > ImSortedSet sortedSet(Iterable items) {
return PersistentTreeSet.of(items);
}
/** Returns a new Tuple2 of the given items. */
public static Tuple2 tup(T t, U u) { return Tuple2.of(t, u); }
/** Returns a new Tuple3 of the given items. */
public static Tuple3 tup(T t, U u, V v) { return Tuple3.of(t, u, v); }
/**
Returns a new PersistentVector of the given items. This data definition method is one of the
three methods in this project that support varargs.
*/
@SafeVarargs
static public ImList vec(T... items) {
if ( (items == null) || (items.length < 1) ) { return PersistentVector.empty(); }
return PersistentVector.ofIter(Arrays.asList(items));
}
/**
If you need to wrap a regular Java collection or other iterable outside this project to perform
a transformation on it, this method is the most convenient, efficient way to do so.
*/
public static Transformable xform(Iterable iterable) { return Xform.of(iterable); }
}