[racket] REPL input chunking for non-sexp language

The datalog language tries to do this too.

There's a repl-submit? predicate you can use and I have weird two-phase
reading system to deal with the EOF issue:

https://github.com/plt/racket/blob/master/collects/datalog/lang/configure-runtime.rkt

https://github.com/plt/racket/blob/master/collects/datalog/tool/submit.rkt

Jay


On Mon, Dec 10, 2012 at 8:04 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:

> When you run plain `racket', the REPL is `read-eval-print-loop', which
> uses `(current-prompt-read)', `(current-eval)', and `(current-print)'.
>
> Any line-editing capability is whatever the terminal does, which
> normally means that input is sent to the reader when you hit Return.
> Even if you load `readline' or `xrepl', a Return commits a line of
> characters to be sent off to the reader.
>
> The delivery of an expression to the evaluator, however, is determined
> by the reader. That is, if your reader sees a "fun" that should match
> an "end", then it should keep reading input characters until it sees
> the "end". When the reader returns a datum, then it's passed off to the
> evaluator.
>
> (If an interactive EOF is needed to terminate a form for your reader,
> that shouldn't necessarily make the REPL quit. The REPL should quit
> only when the reader returns an EOF. So, a reader might consume an
> interactive EOF as a terminator, and then it can continue reading the
> next time around.)
>
> If I remember correctly, DrRacket is a little different. A Return in
> DrRacket takes the text so far and implicitly adds an EOF to the end.
> If the reader applied to that text raises `exn:fail:read:eof', then
> DrRacket it as an indication that the expression isn't finished, and so
> it lets the user keep editing on the next line. Meanwhile, an
> `exn:fail:read' exception other than the subtype `exn:fail:read:eof'
> means that the read error should be reported to the user.
>
>
> At Sun, 9 Dec 2012 19:03:44 -0500, Daniel Patterson wrote:
> > I'm working (with sk and jpolitz) on a non-sexp language built on top
> > of racket.
> >
> > We have basic support for it in the repl inside DrRacket, but none at
> > all from the racket commandline repl (which also means no support for
> > embedding inside other editors) - and the former seems to be using
> > s-exps to figure out when to send the input to our eval (I think - I
> > haven't found documentation describing how this works).
> >
> > So my question is:
> >
> > Is there a way to specify how input is split before sending to eval,
> > both so that DrRacket could follow our conventions (which might, for
> > example, match a "fun" with matching "end"), and so that the
> > commandline repl knows how to split input at all (as right now it just
> > keeps waiting for input until EOF - and EOF also causes the repl to
> > quit!) Is there something that read/read-syntax should signal, or another
> > handler to use?
> >
> > Thanks!
> > Daniel
> > ____________________
> >   Racket Users list:
> >   http://lists.racket-lang.org/users
> ____________________
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>



-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://faculty.cs.byu.edu/~jay

"The glory of God is Intelligence" - D&C 93
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