How are strings freed in ATS2?

Question

http://www.ats-lang.org/Documents.html includes "Introduction to Programming in ATS", which includes the assertion that fileref_get_line_string returns a Strptr1 (a look in filebas.dats shows that it returns a String via strptr2string), and it includes this code:

#include "share/atspre_staload.hats"
#include "share/atspre_staload_libats_ML.hats"

implement main0() = loop() where
  fun loop(): void = let
      val isnot = fileref_isnot_eof(stdin_ref)
    in
    if isnot then let
      val line = fileref_get_line_string(stdin_ref)
      val () = print_string(line)
      val () = strptr_free(line)
    in
      loop()
    end else ()
  end
end

Which throws a type error if the strptr_free line is included. If that line isn't included, the program blatantly leaks memory. Is there current documentation or are there ATS2 examples that show how the fileref_* words are supposed to be used? What is the ATS2 version of the code above?

Answer 1

There are two versions of fileref_get_line_string: one in prelude/filebas and the other in libats/ML/filebas. For getting linear strings, you need the former:

#include
"share/atspre_staload.hats"

implement
main0() = loop() where
  fun
  loop(): void = let
    val
    isnot =
    fileref_isnot_eof(stdin_ref)
  in
    if isnot then let
      val line =
      fileref_get_line_string(stdin_ref)
      val () =
      print_strptr(line)
      val () = free(line)
    in
      loop()
    end else ()
  end
end