From 94a4c538685ddf23e965605970f09d00689c534d Mon Sep 17 00:00:00 2001
From: Rohit Tanwar <mst10041967@gmail.com>
Date: Sat, 27 Jan 2018 11:01:18 +0530
Subject: [PATCH] factorial

---
 README.md             | 29 +++++++++++++++++++++++++++++
 snippets/factorial.md |  6 +++++-
 tag_database          |  1 +
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index f97069ea7..f2c4a8ccf 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,7 @@
 ### :heavy_division_sign: Math
 
 <details><summary>View contents</summary> <ul><li><a href = "#average"><code>average</code></a></li>
+<li><a href = "#factorial"><code>factorial</code></a></li>
 <li><a href = "#gcd"><code>gcd</code></a></li>
 <li><a href = "#lcm"><code>lcm</code></a></li>
 <li><a href = "#max_n"><code>max_n</code></a></li>
@@ -68,6 +69,34 @@ average(1, 2, 3) # 2.0
 
 <br><a href = "#table-of-contents">:arrow_up: Back to top</a>
  
+### factorial
+
+Calculates the factorial of a number.
+
+Use recursion. If `num` is less than or equal to `1`, return `1`. Otherwise, return the product of `num` and the factorial of `num - 1`. Throws an exception if `num` is a negative or a floating point number.
+
+```py 
+
+
+def factorial(num):
+    if not ((num >= 0) & (num % 1 == 0)):
+        raise Exception(
+            f"Number( {num} ) can't be floating point or negative ")
+    return 1 if num == 0 else num * factorial(num - 1)
+
+ 
+ ```
+<details><summary>View Examples</summary>
+
+```py
+
+factorial(6) # 720
+
+```
+</details>
+
+<br><a href = "#table-of-contents">:arrow_up: Back to top</a>
+ 
 ### gcd
 
 :information_source: `math.gcd` works with only two numbers
diff --git a/snippets/factorial.md b/snippets/factorial.md
index bb801131d..a22f2c67f 100644
--- a/snippets/factorial.md
+++ b/snippets/factorial.md
@@ -6,10 +6,14 @@ Use recursion. If `num` is less than or equal to `1`, return `1`. Otherwise, ret
 
 ```python 
 
+
 def factorial(num):
     if not ((num >= 0) & (num % 1 == 0)):
         raise Exception(
             f"Number( {num} ) can't be floating point or negative ")
     return 1 if num == 0 else num * factorial(num - 1)
 
-```
\ No newline at end of file
+```
+``` python
+factorial(6) # 720
+```
diff --git a/tag_database b/tag_database
index bdc88a214..b567d72b5 100644
--- a/tag_database
+++ b/tag_database
@@ -5,6 +5,7 @@ count_occurences:list
 count_vowels:string
 deep_flatten:list
 difference:list
+factorial:math
 gcd:math
 lcm:math
 max_n:math