src/HOL/Library/MLString.thy

       then prefix "\\" (string_of_int i)
       else c
     end;
   val print_string = quote;
 in 
-  CodegenPackage.add_pretty_ml_string "ml" "Nil" "Cons" "STR"
+  CodegenPackage.add_pretty_ml_string "ml" "List.list.Nil" "List.list.Cons" "MLString.ml_string.STR"
     print_char print_string "String.implode"
 end
 *}
 
 code_constapp explode