From: Kevin Ryde <user42@zip.com.au>
Subject: Re: doco ports verbiage
Date: Sun, 15 Jun 2003 10:32:10 +1000 [thread overview]
Message-ID: <877k7ow585.fsf@zip.com.au> (raw)
In-Reply-To: <87k7bp5wj3.fsf@zagadka.ping.de> (Marius Vollmer's message of "14 Jun 2003 02:32:16 +0200")
Marius Vollmer <mvo@zagadka.de> writes:
>
> Or we could stay in Scheme and say it is equivalent to
>
> (open-file FILENAME "w")
Yes, that sounds like the way to go. New effort below, referring to
open-input-file and open-output-file, which strike me as natural
counterparts to these `with' functions.
> and make sure that open-file is documented properly.
I guess it already says the contents are removed (truncated) for "w".
- Scheme Procedure: call-with-input-file filename proc
- Scheme Procedure: call-with-output-file filename proc
Open FILENAME for input or output, and call `(PROC port)' with the
resulting port. Return the value returned by PROC. FILENAME is
opened as per `open-input-file' or `open-output-file'
respectively, and an error is signalled if it cannot be opened.
When PROC returns, the port is closed. If PROC does not return
(eg. if it throws an error), then the port might not be closed
automatically, though it will be garbage collected in the usual
way if not otherwise referenced.
- Scheme Procedure: with-input-from-file filename thunk
- Scheme Procedure: with-output-to-file filename thunk
- Scheme Procedure: with-error-to-file filename thunk
Open FILENAME and call `(THUNK)' with the new port setup as
respectively the `current-input-port', `current-output-port', or
`current-error-port'. Return the value returned by THUNK.
FILENAME is opened as per `open-input-file' or `open-output-file'
respectively, and an error is signalled if it cannot be opened.
When THUNK returns, the port is closed and the previous setting of
the respective current port is restored.
The current port setting is managed with `dynamic-wind', so the
previous value is restored no matter how THUNK exits (eg. an
exception), and if THUNK is re-entered (via a captured
continuation) then it's set again to the FILENAME port.
The port is closed when THUNK returns normally, but not when
exited via an exception or new continuation. This ensures it's
still ready for use if THUNK is re-entered by a captured
continuation. Of course the port is always garbage collected and
closed in the usual way when no longer referenced anywhere.
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next prev parent reply other threads:[~2003-06-15 0:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-06-12 0:56 doco ports verbiage Kevin Ryde
2003-06-12 14:02 ` Marius Vollmer
2003-06-14 0:02 ` Kevin Ryde
2003-06-14 0:32 ` Marius Vollmer
2003-06-15 0:32 ` Kevin Ryde [this message]
2003-06-18 23:39 ` Marius Vollmer
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