Merge pull request #148 from calmm-js/feature/flat

Added `flat`

README.md

@@ -55,6 +55,7 @@ parts.  [Try Lenses!](https://calmm-js.github.io/partial.lenses/playground.html)
       * [`L.traverse(algebra, (maybeValue, index) => operation, optic, maybeData) ~> operation`](#L-traverse "L.traverse: (Functor|Applicative|Monad) c -> ((Maybe a, Index) -> c b) -> POptic s t a b -> Maybe s -> c t") <small><sup>v10.0.0</sup></small>
     * [Nesting](#nesting)
       * [`L.compose(...optics) ~> optic`](#L-compose "L.compose: (POptic s s1, ...POptic sN a) -> POptic s a") or `[...optics]` <small><sup>v1.0.0</sup></small>
+      * [`L.flat(...optics) ~> optic`](#L-flat "L.flat: (POptic s [...s1...], ...POptic sN [...a...]) -> POptic [...s...] a") <small><sup>v13.6.0</sup></small>
     * [Recursing](#recursing)
       * [`L.lazy(optic => optic) ~> optic`](#L-lazy "L.lazy: (POptic s a -> POptic s a) -> POptic s a") <small><sup>v5.1.0</sup></small>
     * [Adapting](#adapting)
@@ -1169,6 +1170,13 @@ first two.
 Note that [`R.compose`](http://ramdajs.com/docs/#compose) is not the same as
 `L.compose`.
 
+##### <a id="L-flat"></a> [≡](#contents) [▶](https://calmm-js.github.io/partial.lenses/index.html#L-flat) [`L.flat(...optics) ~> optic`](#L-flat "L.flat: (POptic s [...s1...], ...POptic sN [...a...]) -> POptic [...s...] a") <small><sup>v13.6.0</sup></small>
+
+`L.flat` is like [`L.compose`](#L-compose) except that [`L.flatten`](#L-flatten)
+is composed around and between the given optics.  In other words, `L.flat(o1,
+..., oN)` is equivalent to `L.compose(L.flatten, o1, L.flatten, ..., L.flatten,
+oN, L.flatten)`.
+
 #### <a id="recursing"></a> [≡](#contents) [▶](https://calmm-js.github.io/partial.lenses/index.html#recursing) [Recursing](#recursing)
 
 The [`L.lazy`](#L-lazy) combinator allows one to build optics that deal with

src/partial.lenses.js

@@ -781,6 +781,13 @@ export function compose() {
   }
 }
 
+export function flat() {
+  const r = [flatten]
+  for (let i = 0, n = arguments.length; i < n; ++i)
+    r.push(arguments[i], flatten)
+  return r
+}
+
 // Recursing
 
 export function lazy(o2o) {

test/tests.js

@@ -232,6 +232,7 @@ describe('arities', () => {
     find: 1,
     findWith: 1,
     first: undefined,
+    flat: 0,
     flatten: 4,
     foldTraversalLens: 2,
     foldl: 4,
@@ -1705,6 +1706,21 @@ describe('L.pointer', () => {
   })
 })
 
+describe('L.flat', () => {
+  testEq(
+    `L.modify(
+      L.flat(
+        'a',
+        'b',
+        'c'
+      ),
+      R.negate,
+      [{a: [[{b: {c: 1}}], [{b: [{c: 2}]}]]}, {a: {b: {c: [[[3]]]}}}]
+    )`,
+    [{a: [[{b: {c: -1}}], [{b: [{c: -2}]}]]}, {a: {b: {c: [[[-3]]]}}}]
+  )
+})
+
 if (process.env.NODE_ENV !== 'production') {
   describe('debug', () => {
     testThrows(`X.set(-1, 0, 0)`)

test/types.js

@@ -93,6 +93,7 @@ export const traverse = T.fn(
 // Nesting
 
 export const compose = T.fnVarN(0, T_optic, T_optic)
+export const flat = T.fnVarN(0, T_optic, T_optic)
 
 // Recursing