David,
The basis library documentation for exception SysErr states:
...but if a SysErr exception has the form SysErr (s, SOME e),
then we have errorMsg e = s.
http://www.standardml.org/Basis/os.html
However, it appears that Poly/ML is not always preserving that property
because errorMsg e and s are sometimes different strings, for example:
val () = ignore (TextIO.openIn "a non-existent file name")
handle
e as IO.Io {cause, ...} => (
case cause of
OS.SysErr (s, SOME e) => (
print "\n";
app print ["s = \"", s, "\"\n"];
app print ["errorMsg e = \"", OS.errorMsg e, "\"\n"]
)
| _ => ()
);
If the Standard is to be followed and one of the messages must be
chosen, the string returned by errorMsg e seems to be the useful one as
s can be deduced from the structure of the program, at least in this
example.
Regards,
Phil
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