diff options
Diffstat (limited to 'src/main/java/bjc/optics/Lenses.java')
| -rw-r--r-- | src/main/java/bjc/optics/Lenses.java | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/src/main/java/bjc/optics/Lenses.java b/src/main/java/bjc/optics/Lenses.java index 6cebc84..aad5571 100644 --- a/src/main/java/bjc/optics/Lenses.java +++ b/src/main/java/bjc/optics/Lenses.java @@ -76,7 +76,7 @@ public class Lenses { public static <Part1, Part2> LensX<Holder<Part1>, Holder<Part2>, Part1, Part2> holder() { return immutable((hld) -> hld.getValue(), (hld, val) -> hld.map((vl) -> val)); } - + /** * Create a lens for updating tagged pairs. * @@ -92,7 +92,13 @@ public class Lenses { public static <A, B, T> LensX<Pair<T, A>, Pair<T, B>, A, B> tagged() { return immutable((par) -> par.getRight(), (par, val) -> par.mapRight((vl) -> val)); } - + + // Not entirely sure what I was thinking when I wrote this. Pretty sure this + // would need W1 to be a monoid to make much sense + // public static <W1, P1, P2> Lens<W1, Pair<P1, P2>> both(Lens<W1, P1> lhs, + // Lens<W1, P2> rhs) { + // } + /** * Creates a lens which focuses on a piece of internal state. * @@ -107,7 +113,7 @@ public class Lenses { Holder<A> hold = Holder.of(val); return immutable((whole) -> hold.getValue(), (whole, vl) -> hold.map((arg) -> vl)); } - + /** * Creates a lens which focuses on a piece of mutable internal state. * @@ -121,6 +127,17 @@ public class Lenses { Holder<A> hold = Holder.of(val); return mutable((whole) -> hold.getValue(), (whole, vl) -> hold.replace(vl)); } + + /** + * Create a lens that focuses on the sign of an integer + * + * @return A lens that focuses on the sign of an integer + */ + public static Lens<Integer, Boolean> sign() { + LensX<Integer, Integer, Boolean, + Boolean> lensX = immutable((num) -> num >= 0, (num, sgn) -> sgn ? Math.abs(num) : -Math.abs(num)); + return (Lens<Integer, Boolean>) lensX; + } } final class FunctionalLensX<W1, W2, P1, P2> implements LensX<W1, W2, P1, P2> { |