Sketch out more modules/protocols

ogstephen · Oct 10, 2015 · f881086 · f881086
1 parent f0e9be7
commit f881086
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Showing 5 changed files with 50 additions and 2 deletions.
diff --git a/lib/witchcraft/arrow.ex b/lib/witchcraft/arrow.ex
@@ -1,3 +1,13 @@
-defmodule Witchcraft.Arrow do
+defprotocol Witchcraft.Arrow do
+  @type arrow :: {any, any, any}
+  @type split :: {any, any}
 
+  @spec arr((any -> any)) :: arrow
+  def arr(b->c)
+
+  @spec first(arrow) :: arrow
+  def first(arrow)
+
+  @spec second(arrow) :: arrow
+  def second(arrow)
 end
diff --git a/lib/witchcraft/arrow/extra.ex b/lib/witchcraft/arrow/extra.ex
@@ -0,0 +1,15 @@
+defmodule Witchcraft.Arrow.Extra do
+  alias Witchcraft.Category, as: C
+  alias Witchcraft.Arrow,    as: A
+
+  @spec product(arrow, arrow) :: arrow
+  def product(f, g) do
+    C.compose_left_to_right(A.first(f), A.second(g))
+  end
+
+  @spec fanout(arrow, arrow) :: arrow
+  def fanout(f, g) do
+    A.arr &({&1, &1})
+    |> C.compose_left_to_right(product(f,g))
+  end
+end
diff --git a/lib/witchcraft/category.ex b/lib/witchcraft/category.ex
@@ -0,0 +1,4 @@
+defprotocol Witchcraft.Category do
+  def id
+  def compose
+end
diff --git a/lib/witchcraft/category/extra.ex b/lib/witchcraft/category/extra.ex
@@ -0,0 +1,11 @@
+defmodule Witchcraft.Category.Extra do
+  alias Witchcraft.Category, as: C
+
+  def compose_left_to_right(a->b, b->c) do
+    &(&1 |> C.compose(a->b) |> C.compose(b->c))
+  end
+
+  def compose_right_to_left(b->c, a->b) do
+    &(&1 |> C.compose(a->b) |> C.compose(b->c))
+  end
+end
diff --git a/lib/witchcraft/monad.ex b/lib/witchcraft/monad.ex
@@ -1,3 +1,11 @@
-defmodule Witchcraft.Monad do
+defprotocol Witchcraft.Monad do
 
+  @spec return(any) :: any
+  def return(bare)
+
+  @spec bind(any, (any -> any)) :: any
+  def bind(wrapped_element, wrapping_func)
+
+  @spec then(any, any) :: any
+  def then(wrapped_element, wrapped_element)
 end