From 1fd87cc33be66900ddd224b2f1ec25139e2678bb Mon Sep 17 00:00:00 2001
From: Ying-Li Niu <64801511@qq.com>
Date: Thu, 11 Jun 2026 19:14:54 +0800
Subject: [PATCH] =?UTF-8?q?fix(fortran):=20=E4=BF=AE=E5=A4=8D=20JSON=20?=
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write_json 中 bond_rest_lengths 后面缺少逗号，
导致 JSON 解码器在 driving_force 前报错：
  JSONDecodeError: Expecting ',' delimiter
将 has_next 从 .false. 改为 .true.，空数组版本也补上逗号。
---
 engines/fortran/main.f90 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/engines/fortran/main.f90 b/engines/fortran/main.f90
index c6c1f46..0d9e909 100644
--- a/engines/fortran/main.f90
+++ b/engines/fortran/main.f90
@@ -1042,11 +1042,11 @@ subroutine write_json(outdir, tx, ty, tz, tvx, tvy, tvz, &
     if (nb > 0) then
         call write_int2_arr(u, 'bond_pairs', bp, nb, .true.)
         call write_dbl_arr(u, 'bond_stiffness', bk, nb, .true.)
-        call write_dbl_arr(u, 'bond_rest_lengths', br, nb, .false.)
+        call write_dbl_arr(u, 'bond_rest_lengths', br, nb, .true.)
     else
         write(u, '(a)') '  "bond_pairs": [],'
         write(u, '(a)') '  "bond_stiffness": [],'
-        write(u, '(a)') '  "bond_rest_lengths": []'
+        write(u, '(a)') '  "bond_rest_lengths": [],'
     end if
 
     write(buf, '(a, i0)') '  "driving_force": ', driving_force