From 2c89a49ba8edf8714fa9a47b4727887db314a43f Mon Sep 17 00:00:00 2001
From: zapashcanon <leo@ndrs.fr>
Date: Mon, 19 Feb 2024 16:54:33 +0100
Subject: [PATCH] use fold_left instead of filteri because it is not available
 on old OCaml versions

---
 src/api/ml/z3.ml | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/api/ml/z3.ml b/src/api/ml/z3.ml
index d26528acb..0be6e57a0 100644
--- a/src/api/ml/z3.ml
+++ b/src/api/ml/z3.ml
@@ -2086,7 +2086,14 @@ struct
 
   let mk_roots (ctx:context) (a:rcf_num list) =
     let n, r = Z3native.rcf_mk_roots ctx (List.length a) a in
-    List.filteri (fun i _v -> i < n) r
+    let _i, l =
+      (* keep only the first `n` elements of the list `r` *)
+      List.fold_left (fun (i, acc) x ->
+        if i = 0 then i, acc
+        else (i - 1, x :: acc)
+      ) (n, []) r
+    in
+    List.rev l
 
   let add (ctx:context) (a:rcf_num) (b:rcf_num) = Z3native.rcf_add ctx a b
   let sub (ctx:context) (a:rcf_num) (b:rcf_num) = Z3native.rcf_sub ctx a b