Add Replace Duplicates In A Keyword List as an elixir til

Author: jbranchaud

README.md

@@ -66,6 +66,7 @@ _330 TILs and counting..._
 ### Elixir
 
 - [Append To A Keyword List](elixir/append-to-a-keyword-list.md)
+- [Replace Duplicates In A Keyword List](elixir/replace-duplicates-in-a-keyword-list.md)
 
 ### Git
 

elixir/replace-duplicates-in-a-keyword-list.md

@@ -0,0 +1,26 @@
+# Replace Duplicates In A Keyword List
+
+Use the
+[`Keyword.put`](http://elixir-lang.org/docs/stable/elixir/Keyword.html#put/3)
+function to replace duplicate key entries in a keyword list.
+
+If there are no duplicate entries, the entry will just be added.
+
+```elixir
+Keyword.put([a: 1], :b, 2)
+[b: 2, a: 1]
+```
+
+If there is a duplicate entry, it will be replaced by the new value.
+
+```elixir
+> Keyword.put([b: 1, a: 1], :b, 2)
+[b: 2, a: 1]
+```
+
+If there are multiple duplicate entries, they will all be replaced.
+
+```elixir
+> Keyword.put([b: 3, b: 4, a: 1], :b, 2)
+[b: 2, a: 1]
+```