chore: update

exm/ballc/ball.zls

@@ -0,0 +1,18 @@
+let g  = 9.81
+let p0 = 5.0
+let v0 = 0.0
+
+let hybrid ball () = (p, z) where
+  rec der p = v    init p0 reset z -> 0.0
+  and der v = -. g init v0 reset z -> -0.8 *. (last v)
+  and z = up (-. p)
+
+let hybrid main () =
+  let der t = 1.0 init 0.0 in
+  let rec der p = 1.0 init -0.01 reset q -> -0.01
+      and q = up (last p) in
+  let (b, z) = ball () in
+  present q | z -> (
+    print_float t; print_string "\t";
+    print_float b; print_newline ()
+  ); ()