Add elixir inspect TIL

README.md

@@ -10,7 +10,7 @@ others" and "this is something really annoying that took forever to find out and
 I know I'll come across it again at some point so I want it committed for
 posterity".
 
-36 TILs and growing!
+37 TILs and growing!
 
 ---
 
@@ -39,6 +39,7 @@ posterity".
 
 - [Base encoding methods](elixir/base-encoding-methods.md)
 - [Get last value in IEx](elixir/get-last-value-in-iex.md)
+- [Inspect with labels](elixir/inspect-with-labels.md)
 - [Releases](elixir/releases.md)
 - [Test coverage](elixir/test-coverage.md)
 - [Test setup](elixir/test-setup.md)

elixir/inspect-with-labels.md

@@ -0,0 +1,30 @@
+# Inspect with labels
+
+`IO.inspect/2` has an option for passing a label to be printed in front of the
+inspected term:
+
+```elixir
+iex(1)> [1, 2, 3] \
+...(1)> |> IO.inspect(label: "before") \
+...(1)> |> Enum.map(&(&1 * 2)) \
+...(1)> |> IO.inspect(label: "after") \
+...(1)> |> Enum.sum()
+before: [1, 2, 3]
+after: [2, 4, 6]
+12
+```
+
+It looks like label can be an atom as well:
+
+```elixir
+iex(2)> defmodule Printer do
+...(2)>   def print(term) do
+...(2)>     IO.inspect(term, label: __MODULE__)
+...(2)>   end
+...(2)> end
+{:module, Printer, <<...>>, {:print, 1}}
+iex(3)> Printer.print(nil)
+Elixir.Printer: nil
+```
+
+[source](https://hexdocs.pm/elixir/IO.html#inspect/2)

structure.json

@@ -5,6 +5,7 @@
   "Elixir": [
     "Base encoding methods",
     "Get last value in IEx",
+    "Inspect with labels",
     "Releases",
     "Test coverage",
     "Test setup",