In freshly started REPL:
Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.24-33-g95b540cb9)
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software.
Please run ?- license. for legal details.
For online help and background, visit https://www.swi-prolog.org
For built-in help, use ?- help(Topic). or ?- apropos(Word).
?- set_prolog_flag(double_quotes,codes).
true.
Now I want to read the man page:
?- help(current_prolog_flag).
ERROR: Type error: `atom' expected, found `[69,110,118,105,114,111,110,109,101,110,116,32,67,111,110,116,114,111,108,32,40,80,114,111,108,111,103,32,102,108,97,103,115,41]' (a list)
ERROR: In:
ERROR: [11] notrace(help_no_trace(current_prolog_flag))
ERROR: [10] prolog_help:help(current_prolog_flag) at /usr/local/logic/swipl/lib/swipl/library/help.pl:136
ERROR: [9] <user>
Ok, this is not impossible, maybe I can go back
?- set_prolog_flag(double_quotes,string).
true.
?- help(current_prolog_flag).
ERROR: Type error: `atom' expected, found `[69,110,118,105,114,111,110,109,101,110,116,32,67,111,110,116,114,111,108,32,40,80,114,111,108,111,103,32,102,108,97,103,115,41]' (a list)
ERROR: In:
ERROR: [11] notrace(help_no_trace(current_prolog_flag))
ERROR: [9] <user>
ERROR:
ERROR: Note: some frames are missing due to last-call optimization.
ERROR: Re-run your program in debug mode (:- debug.) to get more detail.
There is some persistence. Probably cached content that get mangled via the reader?
Not a big problem, but still…