Lens#both specialized for simple lenses

jnape · jnape · commit 1db219c8e5a5 · 2018-05-03T18:22:33.000-05:00
diff --git a/src/main/java/com/jnape/palatable/lambda/lens/Lens.java b/src/main/java/com/jnape/palatable/lambda/lens/Lens.java
@@ -288,6 +288,20 @@ static <S, A, B, C, D> Lens<S, S, Tuple2<A, B>, Tuple2<C, D>> both(Lens<S, S, A,
         return lens(Both.both(view(f), view(g)), (s, cd) -> cd.biMap(set(f), set(g)).into(Fn1::compose).apply(s));
     }
 
+    /**
+     * Dually focus on two simple lenses at the same time.
+     *
+     * @param f   the first lens
+     * @param g   the second lens
+     * @param <S> both larger values
+     * @param <A> both smaller viewing values
+     * @param <B> both smaller setting values
+     * @return the dual-focus simple lens
+     */
+    static <S, A, B> Lens.Simple<S, Tuple2<A, B>> both(Lens.Simple<S, A> f, Lens.Simple<S, B> g) {
+        return adapt(both((Lens<S, S, A, A>) f, g));
+    }
+
     /**
      * A convenience type with a simplified type signature for common lenses with both unified "larger" values and
      * unified "smaller" values.
diff --git a/src/test/java/com/jnape/palatable/lambda/lens/LensTest.java b/src/test/java/com/jnape/palatable/lambda/lens/LensTest.java
@@ -94,4 +94,13 @@ public void bothSplitsFocusBetweenLenses() {
         assertEquals(tuple('a', 3), view(both, "abc"));
         assertEquals("zb", set(both, tuple('z', 2), "abc"));
     }
+
+    @Test
+    public void bothForSimpleLenses() {
+        Lens.Simple<String, Integer> stringToInt = simpleLens(Integer::parseInt, (s, i) -> s + i.toString());
+        Lens.Simple<String, Character> stringToChar = simpleLens(s -> s.charAt(0), (s, c) -> s + c.toString());
+
+        assertEquals(tuple(3, '3'), view(both(stringToInt, stringToChar), "3"));
+        assertEquals("133", set(both(stringToInt, stringToChar), tuple(3, '3'), "1"));
+    }
 }

Original file line number	Diff line number	Diff line change
`@@ -94,4 +94,13 @@ public void bothSplitsFocusBetweenLenses() {`
`94`	`94`	`assertEquals(tuple('a', 3), view(both, "abc"));`
`95`	`95`	`assertEquals("zb", set(both, tuple('z', 2), "abc"));`
`96`	`96`	`}`
	`97`	`+`
	`98`	`+ @Test`
	`99`	`+ public void bothForSimpleLenses() {`
	`100`	`+ Lens.Simple<String, Integer> stringToInt = simpleLens(Integer::parseInt, (s, i) -> s + i.toString());`
	`101`	`+ Lens.Simple<String, Character> stringToChar = simpleLens(s -> s.charAt(0), (s, c) -> s + c.toString());`
	`102`	`+`
	`103`	`+ assertEquals(tuple(3, '3'), view(both(stringToInt, stringToChar), "3"));`
	`104`	`+ assertEquals("133", set(both(stringToInt, stringToChar), tuple(3, '3'), "1"));`
	`105`	`+ }`
`97`	`106`	`}`