From 77fd89e36991abbd02f35e498b874db034abca11 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sat, 16 Dec 2017 18:40:38 +0200
Subject: [PATCH] Added symmetric difference as its own snippet, resolve #168

---
 README.md                              | 17 ++++++++++++++++-
 snippets/array-difference.md           | 10 +---------
 snippets/array-symmetric-difference.md | 11 +++++++++++
 tag_database                           |  1 +
 4 files changed, 29 insertions(+), 10 deletions(-)
 create mode 100644 snippets/array-symmetric-difference.md

diff --git a/README.md b/README.md
index b88fd06c3..af82b8f36 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,7 @@
 * [Array intersection](#array-intersection)
 * [Array remove](#array-remove)
 * [Array sample](#array-sample)
+* [Array symmetric difference](#array-symmetric-difference)
 * [Array union](#array-union)
 * [Array without](#array-without)
 * [Array zip](#array-zip)
@@ -137,7 +138,7 @@ Create a `Set` from `b`, then use `Array.filter()` on `a` to only keep values no
 
 ```js
 const difference = (a, b) => { const s = new Set(b); return a.filter(x => !s.has(x)); };
-// difference([1,2,3], [1,2]) -> [3]
+// difference([1,2,3], [1,2,4]) -> [3]
 ```
 
 [⬆ back to top](#table-of-contents)
@@ -181,6 +182,20 @@ const sample = arr => arr[Math.floor(Math.random() * arr.length)];
 
 [⬆ back to top](#table-of-contents)
 
+### Array symmetric difference
+
+Create a `Set` from each array, then use `Array.filter()` on each of them to only keep values not contained in the other.
+
+```js
+const symmetricDifference = (a, b) => {
+  const sA = new Set(a), sB = new Set(b);
+  return [...a.filter(x => !sB.has(x)), ...b.filter(x => !sA.has(x))];
+}
+// symmetricDifference([1,2,3], [1,2,4]) -> [3,4]
+```
+
+[⬆ back to top](#table-of-contents)
+
 ### Array union
 
 Create a `Set` with all values of `a` and `b` and convert to an array.
diff --git a/snippets/array-difference.md b/snippets/array-difference.md
index b70c2d837..defd82d6f 100644
--- a/snippets/array-difference.md
+++ b/snippets/array-difference.md
@@ -3,14 +3,6 @@
 Create a `Set` from `b`, then use `Array.filter()` on `a` to only keep values not contained in `b`.
 
 ```js
-const difference = (a, b) => { const s = new Set(b); a.filter(x => !s.has(x)); };
+const difference = (a, b) => { const s = new Set(b); return a.filter(x => !s.has(x)); };
 // difference([1,2,3], [1,2,4]) -> [3]
 ```
-
-This function can also be used to generate the symmetric difference or disjunctive union by swapping the
-arrays and combining the results.
-
-```js
-const symmetricDifference = (a, b) => [...difference(a,b), ...difference(b,a)];
-// difference([1,2,3], [1,2,4]) -> [3,4]
-```
diff --git a/snippets/array-symmetric-difference.md b/snippets/array-symmetric-difference.md
new file mode 100644
index 000000000..7d178cd15
--- /dev/null
+++ b/snippets/array-symmetric-difference.md
@@ -0,0 +1,11 @@
+### Array symmetric difference
+
+Create a `Set` from each array, then use `Array.filter()` on each of them to only keep values not contained in the other.
+
+```js
+const symmetricDifference = (a, b) => {
+  const sA = new Set(a), sB = new Set(b);
+  return [...a.filter(x => !sB.has(x)), ...b.filter(x => !sA.has(x))];
+}
+// symmetricDifference([1,2,3], [1,2,4]) -> [3,4]
+```
diff --git a/tag_database b/tag_database
index c833e4f81..6cce617ea 100644
--- a/tag_database
+++ b/tag_database
@@ -4,6 +4,7 @@ array-difference:array
 array-intersection:array
 array-remove:array
 array-sample:array
+array-symmetric-difference:array
 array-union:array
 array-without:array
 array-zip:array