flatten

README.md

@@ -9,7 +9,7 @@
 <p align="center">
   <a href="https://www.npmjs.com/package/tinyfunk"><img src="https://img.shields.io/npm/v/tinyfunk.svg" alt="npm version" style="max-width:100%;"></a>
   <a href="https://www.npmjs.com/package/tinyfunk"><img src="https://img.shields.io/npm/dm/tinyfunk.svg" alt="npm downloads" style="max-width:100%;"></a>
-  <a href="#"><img src="https://img.shields.io/badge/gzip--size-1.49%20kB-blue.svg" alt="gzip-size" style="max-width:100%;"></a>
+  <a href="#"><img src="https://img.shields.io/badge/gzip--size-1.52%20kB-blue.svg" alt="gzip-size" style="max-width:100%;"></a>
   <br />
   <a href="https://travis-ci.org/flintinatux/tinyfunk"><img src="https://travis-ci.org/flintinatux/tinyfunk.svg?branch=master" alt="Build Status" style="max-width:100%;"></a>
   <a href="https://coveralls.io/github/flintinatux/tinyfunk?branch=master"><img src="https://coveralls.io/repos/github/flintinatux/tinyfunk/badge.svg?branch=master" alt="Coverage Status" style="max-width:100%;"></a>
@@ -90,6 +90,7 @@ If you've lived with FP long enough, you are likely familiar with most of the fu
 | `evolve` | `{ k: (v -> v) } -> { k: v } -> { k: v }` |
 | `filter` | `(a -> Boolean) -> [a] -> [a]` |
 | `find` | `(a -> Boolean) -> [a] -> a` |
+| `flatten` | `[a] -> [b]` |
 | `flip` | `(a -> b -> c) -> (b -> a -> c)` |
 | `head` | `[a] -> a` |
 | `identity` | `a -> a` |

src.js

@@ -24,6 +24,10 @@ const _partial = (f, args) =>
 const _putBy = f => (acc, item) =>
   assoc(f(item), item, acc)
 
+// _smash :: ([a], a) -> [b]
+const _smash = (acc, item) =>
+  concat(acc, flatten(item))
+
 // length :: [a] -> Number
 const length = list =>
   list.length
@@ -357,6 +361,10 @@ const pipeP = unapply(flip(reduce(flip(then))))
 // cond :: [[(a -> Boolean), (a -> b)]] -> a -> b
 const cond = compose(reduceRight(thrush, unit), map(apply(ifElse)))
 
+// flatten :: [a] -> [b]
+const flatten =
+  when(Array.isArray, reduce(_smash, []))
+
 // pluck :: k -> [{ k: v }] -> [v]
 const pluck = curry((key, list) =>
   map(prop(key), list)
@@ -419,6 +427,7 @@ _assign(exports, {
   evolve,
   filter,
   find,
+  flatten,
   flip,
   head,
   identity,

test/flatten.js

@@ -0,0 +1,11 @@
+const { expect } = require('chai')
+
+const { flatten } = require('..')
+
+describe('flatten', () => {
+  const arr = [ 1, [ 2, 3 ], [ 4, [ 5 ] ] ]
+
+  it('recursively flattens an array', () =>
+    expect(flatten(arr)).to.eql([ 1, 2, 3, 4, 5 ])
+  )
+})