From 6310540deae1a5e05d46767a35d8ec32865f2c33 Mon Sep 17 00:00:00 2001
From: Dave Coates <david.coates@alliancesoftware.com.au>
Date: Tue, 16 Feb 2016 21:06:27 +1100
Subject: [PATCH] Add support for flatmap

---
 src/list.js      | 19 +++++++++++++++++++
 src/test/list.js | 19 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/src/list.js b/src/list.js
index 53722e4..84c0783 100644
--- a/src/list.js
+++ b/src/list.js
@@ -275,6 +275,25 @@ class TypedList extends BaseTypeInferedList {
       }
     }
   }
+  flatMap(mapper, context) {
+    if (this.size === 0) {
+      return this
+    } else {
+      const result = TypeInferedList.from(this).flatMap(mapper, context)
+      if (this[$store] === result[$store]) {
+        return this
+      }
+      if (result[$type] === this[$type]) {
+        const list = construct(this)
+        list[$store] = result[$store]
+        list.size = result.size
+        return list
+      } else {
+        return result
+      }
+    }
+  }
+
 }
 
 export const List = function(descriptor, label) {
diff --git a/src/test/list.js b/src/test/list.js
index f623fbc..eebc71e 100644
--- a/src/test/list.js
+++ b/src/test/list.js
@@ -985,3 +985,22 @@ test('empty list optimization', assert => {
   assert.equal(Points([Point({x: 1})]).clear(),
                Points([Point({x: 1}), Point({y: 2})]).clear())
 })
+
+test('flatMap', assert => {
+  var numbers = NumberList.of(97, 98, 99);
+  var letters = numbers.flatMap(v => Immutable.fromJS([
+    String.fromCharCode(v),
+    String.fromCharCode(v).toUpperCase(),
+  ]))
+
+  assert.deepEqual(letters.toArray(), ['a','A','b','B','c','C'])
+
+  var letters = numbers.flatMap(v => [
+    String.fromCharCode(v),
+    String.fromCharCode(v).toUpperCase(),
+  ])
+
+  assert.deepEqual(letters.toArray(), ['a','A','b','B','c','C'])
+
+})
+