ADDED: library(prolog_locale) to setup grouped printing of integers.

library/prolog_locale.pl

@@ -0,0 +1,67 @@
+/*  Part of SWI-Prolog
+
+    Author:        Jan Wielemaker
+    E-mail:        [email protected]
+    WWW:           http://www.swi-prolog.org
+    Copyright (c)  2024, SWI-Prolog Solutions b.v.
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions
+    are met:
+
+    1. Redistributions of source code must retain the above copyright
+       notice, this list of conditions and the following disclaimer.
+
+    2. Redistributions in binary form must reproduce the above copyright
+       notice, this list of conditions and the following disclaimer in
+       the documentation and/or other materials provided with the
+       distribution.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+    POSSIBILITY OF SUCH DAMAGE.
+*/
+
+:- module(prolog_locale,
+          [ setup_prolog_locale/0
+          ]).
+
+/** <module> Tweak the locale for Prolog development
+*/
+
+%!  setup_prolog_locale is det.
+%
+%   This sets up  the  locale  to   use  Prolog  friendly  numbers  with
+%   grouping. I.e., after running setup_prolog_locale/0, we get:
+%
+%   ```
+%   ?- A is 1<<100.
+%   A = 1_267_650_600_228_229_401_496_703_205_376.
+%   ```
+
+setup_prolog_locale :-
+    locale_create(_, default,
+                  [ alias(prolog),
+                    decimal_point('.'),
+                    thousands_sep('_'),
+                    grouping([repeat(3)])
+                  ]),
+    set_locale(prolog),
+    add_write_option(answer_write_options, integer_format('~:d')),
+    add_write_option(debug_write_options, integer_format('~:d')),
+    add_write_option(print_write_options, integer_format('~:d')).
+
+add_write_option(Set, Option) :-
+    current_prolog_flag(Set, List),
+    set_prolog_flag(Set, [Option|List]).
+

src/CMakeLists.txt

@@ -160,7 +160,7 @@ set(SWIPL_DATA_library explain.pl sort.pl prolog_config.pl
     prolog_wrap.pl prolog_trace.pl prolog_code.pl intercept.pl
     prolog_deps.pl tables.pl hashtable.pl strings.pl increval.pl
     prolog_debug.pl prolog_versions.pl prolog_evaluable.pl macros.pl
-    prolog_coverage.pl)
+    prolog_coverage.pl prolog_locale.pl)
 if(INSTALL_DOCUMENTATION)
   set(SWIPL_DATA_library ${SWIPL_DATA_library} help.pl)
 endif()