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Adding composition guarantees to LensLike
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‎CHANGELOG.md

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@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
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## [Unreleased]
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### Added
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- `Fn3-8` static factory overloads to aid in coercing lambdas
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- Adding composition guarantees to `LensLike`
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## [3.0.3] - 2018-05-27
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### Added

‎src/main/java/com/jnape/palatable/lambda/lens/Iso.java

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@@ -176,6 +176,11 @@ default <Z> Iso<S, T, A, Z> mapB(Function<? super Z, ? extends B> fn) {
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return unIso().biMapR(f -> f.compose(fn)).into(Iso::iso);
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}
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@Override
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default <C, D> Lens<S, T, C, D> andThen(LensLike<A, B, C, D, ?> f) {
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return toLens().andThen(f);
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}
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/**
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* Left-to-right composition of {@link Iso}.
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*
@@ -200,6 +205,11 @@ default <Q, R> Iso<Q, R, A, B> compose(Iso<Q, R, S, T> g) {
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return g.andThen(this);
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}
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@Override
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default <Q, R> Lens<Q, R, A, B> compose(LensLike<Q, R, S, T, ?> f) {
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return toLens().compose(f);
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}
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/**
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* Static factory method for creating an iso from a function and it's inverse.
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*
@@ -243,23 +253,9 @@ static <S, A> Iso.Simple<S, A> simpleIso(Function<? super S, ? extends A> f, Fun
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* @param <S> the type of both "larger" values
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* @param <A> the type of both "smaller" values
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*/
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@FunctionalInterface
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interface Simple<S, A> extends Iso<S, S, A, A>, LensLike.Simple<S, A, Iso> {
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@Override
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default Iso.Simple<A, S> mirror() {
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return adapt(Iso.super.mirror());
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}
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@Override
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default Lens.Simple<S, A> toLens() {
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return Lens.Simple.adapt(Iso.super.toLens());
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}
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@Override
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default <U> Iso.Simple<S, A> discardR(Applicative<U, LensLike<S, ?, A, A, Iso>> appB) {
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return adapt(Iso.super.discardR(appB));
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}
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/**
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* Compose two simple isos from right to left.
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*
@@ -282,6 +278,31 @@ default <B> Iso.Simple<S, B> andThen(Iso.Simple<A, B> f) {
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return adapt(f.compose(this));
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}
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@Override
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default Iso.Simple<A, S> mirror() {
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return adapt(Iso.super.mirror());
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}
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@Override
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default Lens.Simple<S, A> toLens() {
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return Lens.Simple.adapt(Iso.super.toLens());
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}
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@Override
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default <U> Iso.Simple<S, A> discardR(Applicative<U, LensLike<S, ?, A, A, Iso>> appB) {
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return adapt(Iso.super.discardR(appB));
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}
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@Override
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default <R> Lens.Simple<R, A> compose(LensLike.Simple<R, S, ?> g) {
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return toLens().compose(g);
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}
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@Override
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default <B> Lens.Simple<S, B> andThen(LensLike.Simple<A, B, ?> f) {
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return toLens().andThen(f);
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}
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/**
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* Adapt an {@link Iso} with the right variance to an {@link Iso.Simple}.
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*

‎src/main/java/com/jnape/palatable/lambda/lens/Lens.java

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@@ -220,27 +220,13 @@ default Iso<S, T, A, B> toIso(S s) {
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return iso(view(this), set(this).flip().apply(s));
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}
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/**
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* Left-to-right composition of lenses. Requires compatibility between S and T.
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*
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* @param f the other lens
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* @param <C> the new "smaller" value to read (previously A)
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* @param <D> the new "smaller" update value (previously B)
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* @return the composed lens
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*/
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default <C, D> Lens<S, T, C, D> andThen(Lens<A, B, C, D> f) {
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return f.compose(this);
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@Override
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default <C, D> Lens<S, T, C, D> andThen(LensLike<A, B, C, D, ?> f) {
225+
return lens(view(this).fmap(view(f)), (q, b) -> over(this, set(f, b), q));
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}
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/**
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* Right-to-left composition of lenses. Requires compatibility between A and B.
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*
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* @param g the other lens
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* @param <Q> the new "larger" value for reading (previously S)
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* @param <R> the new "larger" value for putting (previously T)
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* @return the composed lens
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*/
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default <Q, R> Lens<Q, R, A, B> compose(Lens<Q, R, S, T> g) {
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@Override
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default <Q, R> Lens<Q, R, A, B> compose(LensLike<Q, R, S, T, ?> g) {
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return lens(view(g).fmap(view(this)), (q, b) -> over(g, set(this, b), q));
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}
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@@ -323,26 +309,12 @@ static <S, A, B> Lens.Simple<S, Tuple2<A, B>> both(Lens.Simple<S, A> f, Lens.Sim
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@FunctionalInterface
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interface Simple<S, A> extends Lens<S, S, A, A>, LensLike.Simple<S, A, Lens> {
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326-
/**
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* Compose two simple lenses from right to left.
328-
*
329-
* @param g the other simple lens
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* @param <R> the other simple lens' larger type
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* @return the composed simple lens
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*/
333-
default <R> Lens.Simple<R, A> compose(Lens.Simple<R, S> g) {
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default <R> Lens.Simple<R, A> compose(LensLike.Simple<R, S, ?> g) {
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return Lens.Simple.adapt(Lens.super.compose(g));
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}
336315

337-
/**
338-
* Compose two simple lenses from left to right.
339-
*
340-
* @param f the other simple lens
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* @param <B> the other simple lens' smaller type
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* @return the composed simple lens
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*/
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default <B> Lens.Simple<S, B> andThen(Lens.Simple<A, B> f) {
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return f.compose(this);
316+
default <B> Lens.Simple<S, B> andThen(LensLike.Simple<A, B, ?> f) {
317+
return Lens.Simple.adapt(Lens.super.andThen(f));
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}
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/**

‎src/main/java/com/jnape/palatable/lambda/lens/LensLike.java

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Original file line numberDiff line numberDiff line change
@@ -25,6 +25,26 @@ public interface LensLike<S, T, A, B, LL extends LensLike> extends Monad<T, Lens
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<F extends Functor, FT extends Functor<T, F>, FB extends Functor<B, F>> FT apply(
2626
Function<? super A, ? extends FB> fn, S s);
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28+
/**
29+
* Right-to-left composition of lenses. Requires compatibility between A and B.
30+
*
31+
* @param g the other lens
32+
* @param <Q> the new "larger" value for reading (previously S)
33+
* @param <R> the new "larger" value for putting (previously T)
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* @return the composed lens
35+
*/
36+
<Q, R> LensLike<Q, R, A, B, ?> compose(LensLike<Q, R, S, T, ?> g);
37+
38+
/**
39+
* Left-to-right composition of lenses. Requires compatibility between S and T.
40+
*
41+
* @param f the other lens
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* @param <C> the new "smaller" value to read (previously A)
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* @param <D> the new "smaller" update value (previously B)
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* @return the composed lens
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*/
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<C, D> LensLike<S, T, C, D, ?> andThen(LensLike<A, B, C, D, ?> f);
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/**
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* Contravariantly map <code>S</code> to <code>R</code>, yielding a new lens.
3050
*
@@ -117,5 +137,23 @@ default <R> LensLike<R, T, A, B, LL> contraMap(Function<? super R, ? extends S>
117137
* @param <LL> the concrete lens subtype
118138
*/
119139
interface Simple<S, A, LL extends LensLike> extends LensLike<S, S, A, A, LL> {
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141+
/**
142+
* Compose two simple lenses from right to left.
143+
*
144+
* @param g the other simple lens
145+
* @param <R> the other simple lens' larger type
146+
* @return the composed simple lens
147+
*/
148+
<R> LensLike.Simple<R, A, ?> compose(LensLike.Simple<R, S, ?> g);
149+
150+
/**
151+
* Compose two simple lenses from left to right.
152+
*
153+
* @param f the other simple lens
154+
* @param <B> the other simple lens' smaller type
155+
* @return the composed simple lens
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*/
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<B> LensLike.Simple<S, B, ?> andThen(LensLike.Simple<A, B, ?> f);
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}
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}

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