[m-rev.] for review: add system_error_is_success/1

[Julien Fischer]

For review by anyone.

----------------------

Add system_error_is_success/1.

library/io.m:
      As above.

library/io.error_util.m:
      Delete the equivalent operation is_success/1 from here and
      just use system_error_is_success/1 instead.

NEWS.md:
      Announce the new predicate.

Julien.

diff --git a/NEWS.md b/NEWS.md
index c211a7e..f103fe2 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -302,6 +302,7 @@ Changes to the Mercury standard library
      - pred `get_windows_error/2`
      - pred `get_exception_object_error/2`
      - pred `get_system_error_name/2`
+    - pred `system_error_is_success/1`
      - func `init_posn/0`
      - pred `write_binary_string_utf8/3`
      - pred `write_binary_string_utf8/4`
diff --git a/library/io.error_util.m b/library/io.error_util.m
index 3679619..8371dd4 100644
--- a/library/io.error_util.m
+++ b/library/io.error_util.m
@@ -118,35 +118,10 @@
      Error = null;
  ").

-:- pred is_success(system_error::in) is semidet.
-:- pragma inline(pred(is_success/1)).
-
-:- pragma foreign_proc("C",
-    is_success(Error::in),
-    [will_not_call_mercury, promise_pure, thread_safe],
-"
-    // This works for errno and Win32 error values (ERROR_SUCCESS == 0).
-    SUCCESS_INDICATOR = (Error == 0) ? MR_TRUE : MR_FALSE;
-").
-
-:- pragma foreign_proc("C#",
-    is_success(Error::in),
-    [will_not_call_mercury, promise_pure, thread_safe],
-"
-    SUCCESS_INDICATOR = (Error == null);
-").
-
-:- pragma foreign_proc("Java",
-    is_success(Error::in),
-    [will_not_call_mercury, promise_pure, thread_safe],
-"
-    SUCCESS_INDICATOR = (Error == null);
-").
-
  :- pragma inline(pred(is_error/5)).

  is_error(Error, Prefix, MaybeError, !IO) :-
-    ( if is_success(Error) then
+    ( if system_error_is_success(Error) then
          MaybeError = no
      else
          make_io_error_from_system_error_impl(Error, Prefix, IOError, !IO),
@@ -154,7 +129,7 @@ is_error(Error, Prefix, MaybeError, !IO) :-
      ).

  is_error_maybe_win32(Error, IsWin32Error, Prefix, MaybeError, !IO) :-
-    ( if is_success(Error) then
+    ( if system_error_is_success(Error) then
          MaybeError = no
      else
          make_io_error_from_maybe_win32_error(Error, IsWin32Error, Prefix,
@@ -222,7 +197,7 @@ throw_on_close_error(Error, !IO) :-
  throw_on_error(Error, Prefix, !IO) :-
      % This follows the logic of is_error, but does not construct
      % a MaybeError as an intermediate data structure.
-    ( if is_success(Error) then
+    ( if system_error_is_success(Error) then
          true
      else
          make_io_error_from_system_error_impl(Error, Prefix, IOError, !IO),
diff --git a/library/io.m b/library/io.m
index 373329c..b8d1b19 100644
--- a/library/io.m
+++ b/library/io.m
@@ -2147,6 +2147,11 @@
      %
  :- pred get_system_error_name(io.error::in, string::out) is semidet.

+    % Succeeds if the given system error value corresponds to the lack of an
+    % error.
+    %
+:- pred system_error_is_success(io.system_error::in) is semidet.
+
  %---------------------------------------------------------------------------%
  %
  % Instances of the stream typeclasses.
@@ -5037,6 +5042,31 @@ system_error_exception_name(_, _) :-
      error("io.system_error_exception_name: inapplicable back-end").

  %---------------------------------------------------------------------------%
+
+:- pragma inline(pred(system_error_is_success/1)).
+:- pragma foreign_proc("C",
+    system_error_is_success(Error::in),
+    [will_not_call_mercury, promise_pure, thread_safe],
+"
+    // This works for errno and Win32 error values (ERROR_SUCCESS == 0).
+    SUCCESS_INDICATOR = (Error == 0) ? MR_TRUE : MR_FALSE;
+").
+
+:- pragma foreign_proc("C#",
+    system_error_is_success(Error::in),
+    [will_not_call_mercury, promise_pure, thread_safe],
+"
+    SUCCESS_INDICATOR = (Error == null);
+").
+
+:- pragma foreign_proc("Java",
+    system_error_is_success(Error::in),
+    [will_not_call_mercury, promise_pure, thread_safe],
+"
+    SUCCESS_INDICATOR = (Error == null);
+").
+
+%---------------------------------------------------------------------------%
  %---------------------------------------------------------------------------%
  %
  % For use by library.m.