cleaned up code section header, error checking for format-args

src/canary/metta_eval.pl

@@ -1177,19 +1177,19 @@
 get_symbol_metatype(_Vl,'%Undefined%','Symbol').
 get_symbol_metatype(_Vl,_Want,'Grounded').
 
-as_metta_char(X,'#\\'(X)).
-
-eval_20(Eq,RetType,Depth,Self,['stringToChars',String],Chars):- !, eval_args(Eq,RetType,Depth,Self,String,SS), string_chars(SS,Chars0), maplist(as_metta_char,Chars0,Chars).
-eval_20(Eq,RetType,Depth,Self,['charsToString',Chars],String):- !, eval_args(Eq,RetType,Depth,Self,Chars,CC), maplist(as_metta_char,CC0,CC), string_chars(String,CC0).
-
 % =================================================================
 % =================================================================
 % =================================================================
-%  FORMAT-ARGS
+%  STRINGS
 % =================================================================
 % =================================================================
 % =================================================================
 
+as_metta_char(X,'#\\'(X)).
+
+eval_20(Eq,RetType,Depth,Self,['stringToChars',String],Chars):- !, eval_args(Eq,RetType,Depth,Self,String,SS), string_chars(SS,Chars0), maplist(as_metta_char,Chars0,Chars).
+eval_20(Eq,RetType,Depth,Self,['charsToString',Chars],String):- !, eval_args(Eq,RetType,Depth,Self,Chars,CC), maplist(as_metta_char,CC0,CC), string_chars(String,CC0).
+
 % We deal with indexing, but not formatting (the stuff following the ':')(yet)
 % https://doc.rust-lang.org/std/fmt/ used as a reference
 
@@ -1227,10 +1227,14 @@
     format_args(FormatRest3, Iterator2, Args).
 format_args([C|FormatRest], Iterator, Args) :- put(C), format_args(FormatRest, Iterator, Args).
 
-eval_20(Eq,RetType,Depth,Self,['format-args',Format,Args],Result):- !,
+eval_20(Eq,RetType,Depth,Self,['format-args',Format,Args],Result):-
    eval_args(Eq,RetType,Depth,Self,Format,EFormat),
    eval_args(Eq,RetType,Depth,Self,Args,EArgs),
-   is_list(EArgs),string_chars(EFormat, FormatChars), user_io(with_output_to(string(Result), format_args(FormatChars, 0, EArgs))).
+   is_list(EArgs),string_chars(EFormat, FormatChars), !,
+   user_io(with_output_to(string(Result), format_args(FormatChars, 0, EArgs))).
+eval_20(Eq,RetType,Depth,Self,['format-args',_Fmt,Args],_Result) :-
+   eval_args(Eq,RetType,Depth,Self,Args,EArgs),
+   \+ is_list(EArgs),!,throw_metta_return(['Error',Args,'BadType']).
 
 eval_20(Eq,RetType,_Depth,_Self,['flip'],Bool):-
    ignore(RetType='Bool'), !, as_tf(random(0,2,0),Bool),