Add Compute md5 Digest Of A String as an Elixir til

Author: jbranchaud

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
-_501 TILs and counting..._
+_502 TILs and counting..._
 
 ---
 
@@ -87,6 +87,7 @@ _501 TILs and counting..._
 - [Assert An Exception Is Raised](elixir/assert-an-exception-is-raised.md)
 - [Binary Representation Of A String](elixir/binary-representation-of-a-string.md)
 - [Check For A Substring Match](elixir/check-for-a-substring-match.md)
+- [Compute md5 Digest Of A String](elixir/compute-md5-digest-of-a-string.md)
 - [Counting Records With Ecto](elixir/counting-records-with-ecto.md)
 - [Create A Date With The Date Sigil](elixir/create-a-date-with-the-date-sigil.md)
 - [Creating Indexes With Ecto](elixir/creating-indexes-with-ecto.md)

elixir/compute-md5-digest-of-a-string.md

@@ -0,0 +1,20 @@
+# Compute md5 Digest Of A String
+
+To compute the md5 digest of a string, we can use Erlang's top-level `md5`
+function.
+
+```elixir
+> :erlang.md5("#myelixirstatus")
+<<145, 148, 139, 99, 194, 176, 105, 18, 242, 246, 37, 69, 142, 69, 226, 199>>
+```
+
+This, however, gives us the result in the raw binary representation. We
+would like it in a base 16 encoding, as md5 digests tend to be.
+
+We can wrap (or pipe) this with `Base.encode16` to get the result we are
+looking for.
+
+```elixir
+> Base.encode16(:erlang.md5("#myelixirstatus"), case: :lower)
+"91948b63c2b06912f2f625458e45e2c7"
+```