Adds space for letrec, some capture avoidance, remove binder arrows.

1 files changed, 19 insertions, 0 deletions

diff --git a/discocaml/util.ml b/discocaml/util.ml
new file mode 100644
index 0000000..9c70a1a
--- /dev/null
+++ b/discocaml/util.ml
@@ -0,0 +1,19 @@
+let break_to_subscript (s : string) : (string * int) option =
+  let rec loop (i : int) : (string * int) option =
+    if i < 0 then None
+    else
+      let ch = String.get s i in
+      if '0' <= ch && ch <= '9' then loop (i - 1)
+      else
+        let name = String.sub s 0 (i + 1)
+        and sub = String.sub s (i + 1) (String.length s - i - 1) in
+        if sub = "" then None
+        else int_of_string_opt sub |> Option.map (fun i -> (name, i))
+  in
+  loop (String.length s - 1)
+
+let%test "break_to_subscript fail" = break_to_subscript "x1y" = None
+let%test "break_to_subscript simple" = break_to_subscript "x1" = Some ("x", 1)
+let%test "break_to_subscript empty" = break_to_subscript "" = None
+let%test "break_to_subscript number" = break_to_subscript "123" = None
+let%test "break_to_subscript multi" = break_to_subscript "x12" = Some ("x", 12)