1 files changed, 44 insertions, 0 deletions
diff --git a/core/maybe.milch b/core/maybe.milch
new file mode 100644
index 0000000..ef9e906
--- /dev/null
+++ b/core/maybe.milch
@@ -0,0 +1,44 @@
+; LIB
+
+(record Maybe/Just value)
+(record Maybe/Nothing)
+
+(let Maybe/just Maybe/Just/create)
+(let Maybe/nothing Maybe/Nothing/create)
+
+(let Maybe/map (\[f m]
+    (match (kind m)
+        "Maybe/Just" (Maybe/just (f (Maybe/Just/get-value m)))
+        "Maybe/Nothing" (Maybe/nothing))))
+
+(let Maybe/and-then (\[f m]
+    (match (kind m)
+        "Maybe/Just" (f (Maybe/Just/get-value m))
+        "Maybe/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/Just/get-value m)]))
+;;     (Maybe/nothing)
+;;         (print-line! "found nothing!"))
+
+;; (let m (Maybe/just 10))
+;; (pipe m [
+;;     (Maybe/map (+ 5))
+;;     (Maybe/and-then (\[val] (Maybe/just (- val 3))))
+;; ])