From: Markus Triska <triska@metalevel.at>
Date: Thu, 1 May 2025 07:18:00 +0000 (+0200)
Subject: FIXED: correct partial string tail calculation in arg/3
X-Git-Tag: v0.10.0~35^2~16
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=709dc041ebf7cc47d41a05dc35f7a9a18c8d3691;p=scryer-prolog.git

FIXED: correct partial string tail calculation in arg/3

This addresses another aspect of #2924, found by @haijinSk.
Thank you again!

Example:

    ?- "aaaaaaa" = [_,_,_,_,_,_|T], arg(2, T, 2).
       false.
---

diff --git a/src/machine/machine_state_impl.rs b/src/machine/machine_state_impl.rs
index baa25394..038a16d7 100644
--- a/src/machine/machine_state_impl.rs
+++ b/src/machine/machine_state_impl.rs
@@ -933,7 +933,7 @@ impl MachineState {
                                     if char_iter.next().is_some() {
                                         unify_fn!(*self, pstr_loc_as_cell!(pstr_loc + c.len_utf8()), a3);
                                     } else {
-                                        let tail_idx = Heap::pstr_tail_idx(pstr_loc);
+                                        let tail_idx = Heap::pstr_tail_idx(pstr_loc + c.len_utf8());
                                         unify_fn!(*self, self.heap[tail_idx], a3);
                                     }