add lensIso

source/lensIso.js

@@ -0,0 +1,40 @@
+import _curry2 from './internal/_curry2.js';
+import map from './map.js';
+
+
+/**
+ * Returns a lens for the given isomorphic function pairs to/from.
+ * Where we go source `to` focus, then backwards source `from` focus.
+ * The function pairs should never loose data between the structure mappings
+ *
+ * @func
+ * @memberOf R
+ * @since v0.31.0
+ * @category Object
+ * @typedefn Lens s a = Functor f => (a -> f a) -> s -> f s
+ * @sig (s -> a) -> (a -> s) -> Lens s a
+ * @param {Function} to
+ * @param {Function} from
+ * @return {Lens}
+ * @see R.view, R.set, R.over, R.lensIndex, R.lensProp
+ * @example
+ *
+ *      const xJson = lensIso(JSON.parse, JSON.stringify);
+ *
+ *      R.view(xJson, '{"x": 4, "y": 2}'); //=> {x: 4, y: 2}
+ *      R.set(xJson, {x: 4, y: 10 }, '{"x": 4, "y": 2}'); //=> '{"x": 4, "y": 10}'
+ *      R.over(xJson, R.assoc('x', 6), '{"x": 4,"y": 2}'); //=> '{"x": 6 ,"y": 2}'
+ */
+var lensIso = _curry2(function lensIso(to, from) {
+  return function(toFunctorFn) {
+    return function(target) {
+      return map(
+        function(focus) {
+          return from(focus);
+        },
+        toFunctorFn(to(target))
+      );
+    };
+  };
+});
+export default lensIso;