Add maybe concept

1 files changed, 28 insertions, 0 deletions

diff --git a/examples/maybe.lisp b/examples/maybe.lisp
new file mode 100644
index 0000000..ce2cd03
--- /dev/null
+++ b/examples/maybe.lisp
@@ -0,0 +1,28 @@
+; LIB
+
+(let just (\[a]
+    ["maybe" "just" a]))
+(let nothing (\[]
+    ["maybe" "nothing"]))
+
+(let at (\[n seq]
+    (match seq
+        [] (nothing)
+        (match n
+            0 (head seq)
+            (at (- n 1) (tail seq))))))
+
+(let from-just (at 2))
+(let kind (at 1))
+
+(let map (\[f m]
+    (match (kind m)
+        "just" (just (f (from-just m)))
+        "nothing")))
+
+; TESTING
+
+(let m (just 10))
+(match (kind m)
+    "just" (from-just m)
+    "nothing" "nothing")