1 files changed, 51 insertions, 0 deletions
diff --git a/stdlib/maybe.milch b/stdlib/maybe.milch
new file mode 100644
index 0000000..086b0dc
--- /dev/null
+++ b/stdlib/maybe.milch
@@ -0,0 +1,51 @@
+; LIB
+
+(let! Maybe/just (\[a]
+    ["Maybe" "just" a]))
+(let! Maybe/nothing (\[]
+    ["Maybe" "nothing"]))
+
+(let! Maybe/#at (\[n seq]
+    (match seq
+        []
+            (fatal! "Maybe/#at out of bounds")
+        otherwise
+            (match n
+                0
+                    (head seq)
+                otherwise
+                    (Maybe/#at (- n 1) (tail seq))))))
+
+(let! Maybe/unpack (Maybe/#at 2))
+(let! Maybe/kind (Maybe/#at 1))
+
+(let! Maybe/map (\[f m]
+    (match (Maybe/kind m)
+        "just" (Maybe/just (f (Maybe/unpack m)))
+        "nothing" (Maybe/nothing))))
+
+(let! Maybe/and-then (\[f m]
+    (match (Maybe/kind m)
+        "just" (f (Maybe/unpack m))
+        "nothing" (Maybe/nothing))))
+
+; TESTING
+
+;; (let! print-line! (\[s]
+;;     (print! (concat s "\n"))))
+
+;; (let! a (Maybe/just 10))
+;; (let! b (Maybe/nothing))
+
+;; (Maybe/map (+ 5) a)
+;; (Maybe/map (+ 5) b)
+
+;; (Maybe/and-then (\[n] (Maybe/just (+ n 5))) a)
+;; (Maybe/and-then (\[n] (Maybe/just (+ n 5))) b)
+
+;; (let! m (Maybe/just 10))
+;; (match m
+;;     (Maybe/just _)
+;;         (print-line! (fmt "found just {0}!" [(Maybe/unpack m)]))
+;;     (Maybe/nothing)
+;;         (print-line! "found nothing!"))