From 421d7964e5ce397400ce04e69b52f819ed3a64c2 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Wed, 24 Jan 2018 16:22:14 +0200
Subject: [PATCH] Add unfold

Similar to Ramda's unfold
---
 snippets/unfold.md | 20 ++++++++++++++++++++
 tag_database       |  1 +
 2 files changed, 21 insertions(+)
 create mode 100644 snippets/unfold.md

diff --git a/snippets/unfold.md b/snippets/unfold.md
new file mode 100644
index 000000000..ff161aa91
--- /dev/null
+++ b/snippets/unfold.md
@@ -0,0 +1,20 @@
+### unfold
+
+Builds an array, using an iterator function and an initial seed value.
+
+Use a `while` loop and `Array.push()` to call the function repeatedly until it returns `false`.
+The iterator function accepts one argument (`seed`) and must always return an array with two elements ([`value`, `nextSeed`]) or `false` to terminate.
+
+```js
+const unfold = (fn, seed) => {
+  let result = [],
+    val = [null, seed];
+  while ((val = fn(val[1]))) result.push(val[0]);
+  return result;
+};
+```
+
+```js
+var f = n => (n > 50 ? false : [-n, n + 10]);
+unfold(f, 10); // [-10, -20, -30, -40, -50]
+```
diff --git a/tag_database b/tag_database
index c48aed7e1..b5ea61b91 100644
--- a/tag_database
+++ b/tag_database
@@ -230,6 +230,7 @@ truncateString:string
 truthCheckCollection:object,logic,array
 unary:adapter,function
 unescapeHTML:string,browser
+unfold:function,array
 union:array,math
 unionBy:array,function
 unionWith:array,function