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Functional Java is an open source library that supports closures for the Java programming language
package fj;
import fj.control.parallel.Promise;
import fj.data.*;
import static fj.P.p;
import static fj.data.IterableW.wrap;
import static fj.data.Set.iterableSet;
import static fj.data.Tree.node;
import static fj.data.TreeZipper.treeZipper;
import static fj.data.Zipper.zipper;
/**
* Created by MarkPerry on 6/04/2014.
*/
public final class F2Functions {
private F2Functions() {
}
/**
* Partial application.
*
* @param a The A to which to apply this function.
* @return The function partially applied to the given argument.
*/
public static F f(final F2 f, final A a) {
return b -> f.f(a, b);
}
/**
* Curries this wrapped function to a wrapped function of arity-1 that returns another wrapped function.
*
* @return a wrapped function of arity-1 that returns another wrapped function.
*/
public static F> curry(final F2 f) {
return a -> b -> f.f(a, b);
}
/**
* Flips the arguments of this function.
*
* @return A new function with the arguments of this function flipped.
*/
public static F2 flip(final F2 f) {
return (b, a) -> f.f(a, b);
}
/**
* Uncurries this function to a function on tuples.
*
* @return A new function that calls this function with the elements of a given tuple.
*/
public static F, C> tuple(final F2 f) {
return p -> f.f(p._1(), p._2());
}
/**
* Promotes this function to a function on Arrays.
*
* @return This function promoted to transform Arrays.
*/
public static F2, Array, Array> arrayM(final F2 f) {
return (a, b) -> a.bind(b, curry(f));
}
/**
* Promotes this function to a function on Promises.
*
* @return This function promoted to transform Promises.
*/
public static F2, Promise, Promise> promiseM(final F2 f) {
return (a, b) -> a.bind(b, curry(f));
}
/**
* Promotes this function to a function on Iterables.
*
* @return This function promoted to transform Iterables.
*/
public static F2, Iterable, IterableW> iterableM(final F2 f) {
return (a, b) -> IterableW.liftM2(curry(f)).f(a).f(b);
}
/**
* Promotes this function to a function on Lists.
*
* @return This function promoted to transform Lists.
*/
public static F2, List, List> listM(final F2 f) {
return (a, b) -> List.liftM2(curry(f)).f(a).f(b);
}
/**
* Promotes this function to a function on non-empty lists.
*
* @return This function promoted to transform non-empty lists.
*/
public static F2, NonEmptyList, NonEmptyList> nelM(final F2 f) {
return (as, bs) -> NonEmptyList.fromList(as.toList().bind(bs.toList(), f)).some();
}
/**
* Promotes this function to a function on Options.
*
* @return This function promoted to transform Options.
*/
public static F2, Option, Option> optionM(final F2 f) {
return (a, b) -> Option.liftM2(curry(f)).f(a).f(b);
}
/**
* Promotes this function to a function on Sets.
*
* @param o An ordering for the result of the promoted function.
* @return This function promoted to transform Sets.
*/
public static F2, Set, Set> setM(final F2 f, final Ord o) {
return (as, bs) -> {
Set cs = Set.empty(o);
for (final A a : as)
for (final B b : bs)
cs = cs.insert(f.f(a, b));
return cs;
};
}
/**
* Promotes this function to a function on Streams.
*
* @return This function promoted to transform Streams.
*/
public static F2, Stream, Stream> streamM(final F2 f) {
return (as, bs) -> as.bind(bs, f);
}
/**
* Promotes this function to a function on Trees.
*
* @return This function promoted to transform Trees.
*/
public static F2, Tree, Tree> treeM(final F2 f) {
return new F2, Tree, Tree>() {
public Tree f(final Tree as, final Tree bs) {
final F2, Tree, Tree> self = this;
return node(f.f(as.root(), bs.root()), P.lazy(() -> streamM(self).f(as.subForest()._1(), bs.subForest()._1())));
}
};
}
/**
* Promotes this function to zip two arrays, applying the function lock-step over both Arrays.
*
* @return A function that zips two arrays with this function.
*/
public static F2, Array, Array> zipArrayM(final F2 f) {
return (as, bs) -> as.zipWith(bs, f);
}
/**
* Promotes this function to zip two iterables, applying the function lock-step over both iterables.
*
* @return A function that zips two iterables with this function.
*/
public static F2, Iterable, Iterable> zipIterableM(final F2 f) {
return (as, bs) -> wrap(as).zipWith(bs, f);
}
/**
* Promotes this function to zip two lists, applying the function lock-step over both lists.
*
* @return A function that zips two lists with this function.
*/
public static F2, List, List> zipListM(final F2 f) {
return (as, bs) -> as.zipWith(bs, f);
}
/**
* Promotes this function to zip two streams, applying the function lock-step over both streams.
*
* @return A function that zips two streams with this function.
*/
public static F2, Stream, Stream> zipStreamM(final F2 f) {
return (as, bs) -> as.zipWith(bs, f);
}
/**
* Promotes this function to zip two non-empty lists, applying the function lock-step over both lists.
*
* @return A function that zips two non-empty lists with this function.
*/
public static F2, NonEmptyList, NonEmptyList> zipNelM(final F2 f) {
return (as, bs) -> NonEmptyList.fromList(as.toList().zipWith(bs.toList(), f)).some();
}
/**
* Promotes this function to zip two sets, applying the function lock-step over both sets.
*
* @param o An ordering for the resulting set.
* @return A function that zips two sets with this function.
*/
public static F2, Set, Set> zipSetM(final F2 f, final Ord o) {
return (as, bs) -> iterableSet(o, as.toStream().zipWith(bs.toStream(), f));
}
/**
* Promotes this function to zip two trees, applying the function lock-step over both trees.
* The structure of the resulting tree is the structural intersection of the two trees.
*
* @return A function that zips two trees with this function.
*/
public static F2, Tree, Tree> zipTreeM(final F2 f) {
return new F2, Tree, Tree>() {
public Tree f(final Tree ta, final Tree tb) {
final F2, Tree, Tree> self = this;
return node(f.f(ta.root(), tb.root()), P.lazy(() -> zipStreamM(self).f(ta.subForest()._1(), tb.subForest()._1())));
}
};
}
/**
* Promotes this function to zip two zippers, applying the function lock-step over both zippers in both directions.
* The structure of the resulting zipper is the structural intersection of the two zippers.
*
* @return A function that zips two zippers with this function.
*/
public static F2, Zipper, Zipper> zipZipperM(final F2 f) {
return (ta, tb) -> {
final F2, Stream, Stream> sf = zipStreamM(f);
return zipper(sf.f(ta.lefts(), tb.lefts()), f.f(ta.focus(), tb.focus()), sf.f(ta.rights(), tb.rights()));
};
}
/**
* Promotes this function to zip two TreeZippers, applying the function lock-step over both zippers in all directions.
* The structure of the resulting TreeZipper is the structural intersection of the two TreeZippers.
*
* @return A function that zips two TreeZippers with this function.
*/
public static F2, TreeZipper, TreeZipper> zipTreeZipperM(final F2 f) {
return (ta, tb) -> {
final F2>, Stream>, Stream>> sf = zipStreamM(treeM(f));
final
F2>, A, Stream>>>,
Stream>, B, Stream>>>,
Stream>, C, Stream>>>>
pf =
zipStreamM((pa, pb) -> p(zipStreamM(treeM(f)).f(pa._1(), pb._1()), f.f(pa._2(), pb._2()),
zipStreamM(treeM(f)).f(pa._3(), pb._3())));
return treeZipper(treeM(f).f(ta.p()._1(), tb.p()._1()), sf.f(ta.lefts(), tb.lefts()),
sf.f(ta.rights(), tb.rights()), pf.f(ta.p()._4(), tb.p()._4()));
};
}
public static F2 contramapFirst(F2 target, F f) {
return (z, b) -> target.f(f.f(z), b);
}
public static F2 contramapSecond(F2 target, F f) {
return (a, z) -> target.f(a, f.f(z));
}
public static F2 contramap(F2 target, F f, F g) {
return contramapSecond(contramapFirst(target, f), g);
}
public static F2 map(F2 target, F f) {
return (a, b) -> f.f(target.f(a, b));
}
}