Add Same Functions Should Be Grouped Together as an elixir til

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/).
 
-_493 TILs and counting..._
+_494 TILs and counting..._
 
 ---
 
@@ -107,6 +107,7 @@ _493 TILs and counting..._
 - [Root Directory Of A Project](elixir/root-directory-of-a-project.md)
 - [Round Floats To Integers](elixir/round-floats-to-integers.md)
 - [Run ExUnit Tests In A Deterministic Order](elixir/run-exunit-tests-in-a-deterministic-order.md)
+- [Same Functions Should Be Grouped Together](elixir/same-functions-should-be-grouped-together.md)
 - [String Interpolation With Just About Anything](elixir/string-interpolation-with-just-about-anything.md)
 - [Updating Values In A Map](elixir/updating-values-in-a-map.md)
 - [Virtual Fields With Ecto Schemas](elixir/virtual-fields-with-ecto-schemas.md)

elixir/same-functions-should-be-grouped-together.md

@@ -0,0 +1,30 @@
+# Same Functions Should Be Grouped Together
+
+A favorite feature of Elixir is the function clauses that can be defined in
+multiple ways with pattern matching. I've always grouped same-named function
+clauses together. It seems like good form and it's what I see everyone else
+doing. It also makes for readable, maintainable code.
+
+This is more than just personal preference though. It is the correct,
+idiomatic way to organize your Elixir function clauses. The compiler will
+let you know if anything gets out of place.
+
+Consider the following snippet of code:
+
+```elixir
+defmodule MeterToLengthConverter do
+  def convert(:feet, m), do: m * 3.28084
+  def convert(:inch, m), do: m * 39.3701
+  def hello(), do: IO.puts "Hello, World!"
+  def convert(:yard, m), do: m * 1.09361
+end
+```
+
+It is syntactically correct, so it will compile. However, the compiler will
+emit a warning like the following:
+
+```
+warning: clauses for the same def should be grouped together, def convert/2
+was previously defined (length_converter.ex:2)
+  length_converter.ex:5
+```