provide read_term_from_chars/2 (#334)

src/prolog/lib/charsio.pl

@@ -1,4 +1,22 @@
-:- module(charsio, [write_term_to_chars/3]).
+:- module(charsio, [read_term_from_chars/2,
+                    write_term_to_chars/3]).
+
+:- use_module(library(iso_ext)).
+
+read_term_from_chars(Chars, Term) :-
+    (  var(Chars) ->
+       throw(error(instantiation_error, read_term_from_chars/2))
+    ;  nonvar(Term) ->
+       throw(error(uninstantiation_error(Term), read_term_from_chars/2))
+    ;  '$skip_max_list'(_, -1, Chars, Chars0),
+       Chars0 == [],
+       partial_string(Chars) ->
+       true
+    ;
+       throw(error(type_error(complete_string, Chars), read_term_from_chars/2))
+    ),
+    '$read_term_from_chars'(Chars, Term).
+
 
 write_term_to_chars(_, Options, _) :-
     var(Options), throw(error(instantiation_error, write_term_to_chars/3)).