[plt-scheme] (thread read)

From: Robby Findler (robby at cs.uchicago.edu)
Date: Thu Jun 7 12:57:34 EDT 2007

As it turns out, drscheme doesn't quite do that. Drscheme separates
the user input from the REPL input and, in the program below, actually
never sends anything to the thread, because the printing of a new
prompt erases the input box.

This is because DrScheme's REPL doesn't read from current-input-port

But, that's what happens in mzscheme or mred's repl (or in other
contexts) -- only drscheme's repl is special.


On 6/7/07, Jens Axel Søgaard <jensaxel at soegaard.net> wrote:
> Chongkai Zhu skrev:
> > What is
> >
> > (thread read)
> >
> > suppose to do? Trying on both DrScheme and MzScheme, version 370 [3m], I
> > got different effects (in DrScheme, even different from run to run).
> >
> > Doing more experiments in DrScheme only confuse me more. Could anyone
> > help clarify? Thanks.
> The original thread (the REPL) and the new thread share the input port.
> When you type something at the REPL either the REPL *or* the new thread
> will read it. If the thread reads it, nothing happens. If the
> REPL reads it it gets evaluated as usual.
> If the REPL reads part of an expression and the threads read some
> then...
> Compare:
> (parameterize
>      ([current-input-port
>          (open-input-string "This is read by the thread")])
>    (thread (lambda ()
>      (display (read)))))
> --
> Jens Axel Søgaard
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