towards #221 by adding a value --vn to command lines turns on the bug…

…fix.. but this adds some slight dangers to be discussed later

prolog/metta_lang/metta_interp.pl

@@ -411,6 +411,7 @@
 option_value_name_default_type_help('answer-format', 'show', ['rust', 'silent', 'detailed'], "Control how results are displayed", 'Output and Logging').
 option_value_name_default_type_help('repeats', true, [true, false], "false to avoid repeated results", 'Miscellaneous').
 option_value_name_default_type_help('time', true, [false, true], "Enable or disable timing for operations (in Rust compatibility mode, this is false)", 'Miscellaneous').
+option_value_name_default_type_help('vn', auto, [auto, true, false], "Enable or disable, (auto = enable but not if it breaks stuff) EXPERIMENTAL BUG-FIX where variable names are preserved (see https://github.com/trueagi-io/metta-wam/issues/221)", 'Miscellaneous').
 
 % Testing and Validation
 option_value_name_default_type_help('synth-unit-tests', false, [false, true], "Synthesize unit tests", 'Testing and Validation').

prolog/metta_lang/metta_loader.pl

@@ -3347,7 +3347,20 @@
 %   @arg NamedVarsList The list of named variables.
 %
 subst_vars(TermWDV, NewTerm, NamedVarsList) :-
-              subst_vars(TermWDV, NewTerm, [], NamedVarsList).
+      subst_vars(TermWDV, NewTerm, [], NamedVarsList),
+   if_t(fast_option_value('vn', 'true'), memorize_varnames(NamedVarsList)).
+
+
+memorize_varnames(NamedVarsList):- \+ compound(NamedVarsList),!.
+memorize_varnames([NamedVar|NamedVarsList]):- !,
+  memorize_varname(NamedVar),
+  memorize_varnames(NamedVarsList).
+memorize_varnames(_).
+memorize_varname(NamedVar):-  \+ compound(NamedVar),!.
+memorize_varname(Name=Var):- var(Var),atomic(Name),put_attr(Var,vn,Name).
+memorize_varname(_).
+
+
 
 %!  subst_vars(+Term, -Term, +Acc, -NamedVarsList) is det.
 %

prolog/metta_lang/metta_printer.pl

@@ -554,13 +554,13 @@
 %
 write_dvar(S) :-
     % If S is an underscore, output the name directly.
-    S == '_', !, write_dname(S).
+    S == '_', !, write('$_').
 write_dvar(S) :-
     % If S is a double underscore, write `$` to represent it.
     S == '__', !, write('$').
 write_dvar(S) :-
     % For an unbound variable, get its name and write it.
-    var(S), get_var_name(S, N), write_dname(N), !.
+    var(S), get_var_name(S, N), write_dvar(N), !.
 write_dvar(S) :-
     % For an unbound variable without a name, format it as `$<variable>`.
     var(S), !, format('$~p', [S]).

prolog/metta_lang/metta_repl.pl

@@ -1473,7 +1473,11 @@
 %
 write_bsrc(Var):- Var=='Empty',!,write(Var).  % Special case: write 'Empty' directly.
 write_bsrc(Var):- ground(Var),!,write_bsrc1(Var).  % If the variable is ground, write it directly.
-write_bsrc(Var):- copy_term(Var,Copy,Goals),Var=Copy,write_bsrc_goal(Var,Goals).  % For non-ground terms, handle goals.
+write_bsrc(Var):- copy_term(Var,Copy,Goals),Var=Copy,
+  exclude(excluded_hidden_goal,Goals,UnhiddenGoals),
+  write_bsrc_goal(Var,UnhiddenGoals).  % For non-ground terms, handle goals.
+
+excluded_hidden_goal(name_variable(_,_)).
 
 %!  write_bsrc_goal(+Var, +Goals) is det.
 %