New order for koans

Equalities
Arithmetic
Strings
Tuples
Lists
Maps
Structs
PatternMatching
Functions
Enums
Processes
Tasks

lib/koans/07_structs.ex

@@ -0,0 +1,55 @@
+defmodule Structs do
+  use Koans
+
+  defmodule Person do
+    defstruct [:name, :age ]
+  end
+
+  koan "structs are defined and named after a module" do
+    person = %Person{}
+    assert person == :__
+  end
+
+  koan "you can access the fields of a struct" do
+    nobody = %Person{}
+    assert nobody.age == :__
+  end
+
+  koan "You can pass initial values to structs" do
+    joe = %Person{name: "Joe", age: 23}
+    assert joe.name == :__
+  end
+
+  koan "update fields with the pipe '|' operator" do
+    joe = %Person{name: "Joe", age: 23}
+    older = %{ joe | age: joe.age + 10}
+    assert  older.age == :__
+  end
+
+  koan "the original struct is not affected by updates" do
+    joe = %Person{name: "Joe", age: 23}
+    assert %{ joe | age: joe.age + 10}.age == 33
+    assert joe.age == :__
+  end
+
+  koan "you can pattern match into the fields of a struct" do
+    %Person{age: age} = %Person{age: 22, name: "Silvia"}
+    assert age == :__
+  end
+
+  defmodule Plane do
+    defstruct passengers: 0, maker: :boeing
+  end
+
+  koan "or onto the type of the struct itself" do
+    assert is_a_plane(%Plane{passengers: 417, maker: :boeing}) == :__
+  end
+
+  def is_a_plane(%Plane{}), do: true
+
+  koan "are basically maps" do
+    silvia = %Person{age: 22, name: "Silvia"}
+
+    assert Map.fetch!(silvia, :age) == :__
+  end
+end