Michael,
I adapted this from an analogous function is_term_in that we have in ProofPower
and it seems to work.
fun is_term_out (outstream : TextIO.outstream) = (
let val (wr as TextPrimIO.WR{ioDesc,...},buf) =
TextIO.StreamIO.getWriter(TextIO.getOutstream
outstream);
val _ = TextIO.setOutstream
(outstream, TextIO.StreamIO.mkOutstream(wr,
buf));
in case ioDesc of
NONE => false
| SOME desc => (OS.IO.kind desc = OS.IO.Kind.tty)
end
);
For reasons that I don’t claim to understand, the stream behaves as if it is
closed
after the call to getWriter. You have to use setOutstream (or setInstream in
is_term_in)
to fix that before anything (e.g., the read-eval-print loop) attempts to do I/O
on the stream.
Regards,
Rob.
> On 7 May 2016, at 06:01, Michael Norrish <[email protected]> wrote:
>
> The Basis library documentation for OS.IO suggests that it should be possible
> to get one's hand on a primitive reader or writer iodesc by pulling things
> apart to get PrimIO values.
>
> Doing type-directed programming, I thought I might do this for a
> TextIO.outstream with
>
>> val getIOD = (fn TextPrimIO.WR r => #ioDesc r) o #1 o
>> TextIO.StreamIO.getWriter o TextIO.getOutstream;
> val getIOD = fn: TextIO.outstream -> OS.IO.iodesc option
>
> This has the right type (and I couldn't see any other way of getting the
> right type). Unfortunately, I can't run it:
>
>> getIOD TextIO.stdOut;
> Exception Io raised while writing to stdOut.
>
> terminating the session.
>
> If this had worked, I then hoped to be able to call Posix.FileSys.iodToFD on
> the value, if there was one, and to then eventually call Posix.ProcEnv.isatty
> on the result of that, if present.
>
> Is there a right way to do this?
>
> Many thanks,
> Michael
>
>
>
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