3 files changed, 43 insertions, 0 deletions
diff --git a/examples/category-theory/Adjoints.gf b/examples/category-theory/Adjoints.gf
new file mode 100644
index 000000000..cb4c8c6c0
--- /dev/null
+++ b/examples/category-theory/Adjoints.gf
@@ -0,0 +1,11 @@
+abstract Adjoints = NaturalTransform ** {
+
+cat Adjoints ({c1,c2} : Category) (Functor c1 c2) (Functor c2 c1) ;
+
+data adjoints : ({c1,c2} : Category)
+              -> (f : Functor c1 c2)
+              -> (g : Functor c2 c1)
+              -> NT (idF c1) (compF g f)
+              -> Adjoints f g ;
+
+}
+\ No newline at end of file
diff --git a/examples/category-theory/CategoryTheory.gf b/examples/category-theory/CategoryTheory.gf
index d079c53b1..6e3ed3e09 100644
--- a/examples/category-theory/CategoryTheory.gf
+++ b/examples/category-theory/CategoryTheory.gf
@@ -5,5 +5,7 @@ abstract CategoryTheory
   , Functor
   , NaturalTransform
   , Equalizer
+  , Adjoints
+  , Monad
 ** {
 }
 \ No newline at end of file
diff --git a/examples/category-theory/Monad.gf b/examples/category-theory/Monad.gf
new file mode 100644
index 000000000..68612d312
--- /dev/null
+++ b/examples/category-theory/Monad.gf
@@ -0,0 +1,30 @@
+abstract Monad = Adjoints ** {
+
+cat Monad ({c} : Category) (m : Functor c c) ;
+
+data monad :  ({c} : Category)
+           -> (m : Functor c c)
+           -> NT (compF m m) m
+           -> NT (idF c) m
+           -> Monad m ;
+
+fun adjoints2monad :  ({c,d} : Category)
+                   -> (f : Functor c d)
+                   -> (g : Functor d c)
+                   -> Adjoints f g
+                   -> Monad (compF g f) ;
+-- def adjoints2monad = ...
+
+{-
+fun kleisliCat :  ({c} : Category)
+               -> ({m} : Functor c c)
+               -> Monad m
+               -> Category ;
+
+fun monad2adjoints :  ({c} : Category)
+                   -> ({m} : Functor c c)
+                   -> Monad m
+                   -> Adjoints {c} {kleisliCat m} f g
+-}
+
+}
+\ No newline at end of file