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Commitc72ef91

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Lens#both for dually focusing with two lenses at once
1 parent6a1ca16 commitc72ef91

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‎CHANGELOG.md

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@@ -23,6 +23,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
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-`Span`, for splitting an`Iterable` into contiguous elements matching a predicate
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-`MagnetizeBy` and`Magnetize`, for grouping elements by pairwise predicate tests
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-`Both`, for dually applying two functions and producing a`Tuple2` of their results
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-`Lens#both`, for dually focusing with two lenses at once
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###Deprecated
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-`Either#trying` in favor of`Try#trying`

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

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packagecom.jnape.palatable.lambda.lens;
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importcom.jnape.palatable.lambda.adt.hlist.Tuple2;
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importcom.jnape.palatable.lambda.functions.Fn1;
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importcom.jnape.palatable.lambda.functions.Fn2;
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importcom.jnape.palatable.lambda.functions.builtin.fn2.Both;
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importcom.jnape.palatable.lambda.functor.Applicative;
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importcom.jnape.palatable.lambda.functor.Functor;
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importcom.jnape.palatable.lambda.functor.Profunctor;
@@ -311,6 +314,23 @@ static <S, A> Lens.Simple<S, A> simpleLens(Function<? super S, ? extends A> gett
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returnadapt(lens(getter,setter));
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}
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/**
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* Dually focus on two lenses at the same time. Requires <code>S</code> and <code>T</code> to be invariant between
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* lenses.
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*
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* @param f the first lens
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* @param g the second lens
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* @param <S> both larger values
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* @param <A> f's smaller viewing value
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* @param <B> g's smaller viewing value
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* @param <C> f's smaller setting value
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* @param <D> g's smaller setting value
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* @return the dual-focus lens
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*/
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static <S,A,B,C,D>Lens<S,S,Tuple2<A,B>,Tuple2<C,D>>both(Lens<S,S,A,C>f,Lens<S,S,B,D>g) {
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returnlens(Both.both(view(f),view(g)), (s,cd) ->cd.biMap(set(f),set(g)).into(Fn1::compose).apply(s));
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}
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/**
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* A convenience type with a simplified type signature for common lenses with both unified "larger" values and
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* unified "smaller" values.
@@ -335,11 +355,32 @@ default <B> Lens.Simple<S, B> andThen(Lens.Simple<A, B> f) {
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returnf.compose(this);
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}
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/**
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* Adapt a {@link Lens} with the right variance to a {@link Lens.Simple}.
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*
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* @param lens the lens
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* @param <S> S/T
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* @param <A> A/B
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* @return the simple lens
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*/
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@SuppressWarnings("unchecked")
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static <S,A>Simple<S,A>adapt(Lens<S,S,A,A>lens) {
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returnlens::apply;
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}
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/**
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* Specialization of {@link Lens#both(Lens, Lens)} for simple lenses.
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*
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* @param f the first lens
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* @param g the second lens
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* @param <S> both lens larger values
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* @param <A> both lens smaller values
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* @return the dual-focus simple lens
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*/
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static <S,A>Lens.Simple<S,Tuple2<A,A>>both(Lens<S,S,A,A>f,Lens<S,S,A,A>g) {
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returnadapt(Lens.both(f,g));
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}
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/**
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* A convenience type with a simplified type signature for fixed simple lenses.
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*

‎src/test/java/com/jnape/palatable/lambda/lens/LensTest.java

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packagecom.jnape.palatable.lambda.lens;
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importcom.jnape.palatable.lambda.adt.Maybe;
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importcom.jnape.palatable.lambda.adt.hlist.Tuple2;
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importcom.jnape.palatable.lambda.functions.Fn1;
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importcom.jnape.palatable.lambda.functor.builtin.Const;
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importcom.jnape.palatable.lambda.functor.builtin.Identity;
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importjava.util.Set;
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importstaticcom.jnape.palatable.lambda.adt.Maybe.just;
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importstaticcom.jnape.palatable.lambda.adt.hlist.HList.tuple;
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importstaticcom.jnape.palatable.lambda.lens.Lens.both;
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importstaticcom.jnape.palatable.lambda.lens.Lens.lens;
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importstaticcom.jnape.palatable.lambda.lens.Lens.simpleLens;
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importstaticcom.jnape.palatable.lambda.lens.functions.Set.set;
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importstaticcom.jnape.palatable.lambda.lens.functions.View.view;
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importstaticjava.lang.Integer.parseInt;
@@ -89,4 +93,14 @@ public void andThenComposesInReverse() {
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assertEquals("one",view(EARLIER_LENS.andThen(LENS),map));
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assertEquals(singletonMap("foo",singleton(1)),set(EARLIER_LENS.andThen(LENS),1,map));
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}
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@Test
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publicvoidbothSplitsFocusBetweenLenses() {
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Lens<String,String,Character,Character>firstChar =simpleLens(s ->s.charAt(0), (s,c) ->c +s.substring(1));
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Lens<String,String,Integer,Integer>length =simpleLens(String::length, (s,k) ->s.substring(0,k));
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Lens<String,String,Tuple2<Character,Integer>,Tuple2<Character,Integer>>both =both(firstChar,length);
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assertEquals(tuple('a',3),view(both,"abc"));
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assertEquals("zb",set(both,tuple('z',2),"abc"));
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}
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}

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