Remove arithmetic koans

lib/koans/07_pattern_matching.ex

@@ -0,0 +1,76 @@
+defmodule PatternMatching do
+  use Koans
+
+  koan "One matches one" do
+    assert match?(1, :__)
+  end
+
+  koan "A pattern can change" do
+    a = 1
+    assert a = :__
+  end
+
+  koan "A pattern can also be strict" do
+    a = 1
+    assert ^a = :__
+  end
+
+  koan "Patterns can be used to pull things apart" do
+    [head | tail] = [1,2,3,4]
+
+    assert head == :__
+    assert tail == :__
+  end
+
+  koan "And then put them back together" do
+    head = 1
+    tail = [2,3,4]
+
+    assert :__ == [head | tail]
+  end
+
+  koan "Some values can be ignored" do
+    [_first, _second, third, _fourth] = [1,2,3,4]
+
+    assert third == :__
+  end
+
+  koan "Strings come apart just a easily" do
+    "Shopping list: " <> items = "Shopping list: eggs, milk"
+
+    assert items == :__
+  end
+
+  koan "Patterns show what you really care about" do
+    %{make: make} = %{type: "car", year: 2016, make: "Honda", color: "black"}
+
+    assert make == :__
+  end
+
+  koan "The pattern can make assertions about what it expects" do
+    assert match?([1, _second, _third], :__)
+  end
+
+  def make_noise(%{type: "cat"}), do: "Meow"
+  def make_noise(%{type: "dog"}), do: "Woof"
+  def make_noise(_anything), do: "Eh?"
+
+  koan "Functions can declare what kind of arguments they accept" do
+    dog = %{type: "dog", legs: 4, age: 9, color: "brown"}
+    cat = %{type: "cat", legs: 4, age: 3, color: "grey"}
+    snake = %{type: "snake", legs: 0, age: 20, color: "black"}
+
+    assert make_noise(dog) == :__
+    assert make_noise(cat) == :__
+    assert make_noise(snake) == :__
+  end
+
+  koan "Errors are shaped differently than sucessful results" do
+    result = case Map.fetch(%{}, :obviously_not_a_key) do
+      :error -> "not present"
+      _ -> flunk("I should not happen")
+    end
+
+    assert result == :__
+  end
+end