Why do you need a weird two-phase reading system to deal with the EOF issue?<div><br></div><div>Robby<br><br>On Monday, December 10, 2012, Jay McCarthy wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> The datalog language tries to do this too.<div><br></div><div>There's a repl-submit? predicate you can use and I have weird two-phase reading system to deal with the EOF issue:</div><div><br></div><div><a href="https://github.com/plt/racket/blob/master/collects/datalog/lang/configure-runtime.rkt" target="_blank">https://github.com/plt/racket/blob/master/collects/datalog/lang/configure-runtime.rkt</a><br> </div><div><br></div><div><a href="https://github.com/plt/racket/blob/master/collects/datalog/tool/submit.rkt" target="_blank">https://github.com/plt/racket/blob/master/collects/datalog/tool/submit.rkt</a><br></div><div> <br></div><div>Jay</div> <div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Dec 10, 2012 at 8:04 AM, Matthew Flatt <span dir="ltr"><<a href="javascript:_e({}, 'cvml', 'mflatt@cs.utah.edu');" target="_blank">mflatt@cs.utah.edu</a>></span> wrote:<br> <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">When you run plain `racket', the REPL is `read-eval-print-loop', which<br> uses `(current-prompt-read)', `(current-eval)', and `(current-print)'.<br> <br> Any line-editing capability is whatever the terminal does, which<br> normally means that input is sent to the reader when you hit Return.<br> Even if you load `readline' or `xrepl', a Return commits a line of<br> characters to be sent off to the reader.<br> <br> The delivery of an expression to the evaluator, however, is determined<br> by the reader. That is, if your reader sees a "fun" that should match<br> an "end", then it should keep reading input characters until it sees<br> the "end". When the reader returns a datum, then it's passed off to the<br> evaluator.<br> <br> (If an interactive EOF is needed to terminate a form for your reader,<br> that shouldn't necessarily make the REPL quit. The REPL should quit<br> only when the reader returns an EOF. So, a reader might consume an<br> interactive EOF as a terminator, and then it can continue reading the<br> next time around.)<br> <br> If I remember correctly, DrRacket is a little different. A Return in<br> DrRacket takes the text so far and implicitly adds an EOF to the end.<br> If the reader applied to that text raises `exn:fail:read:eof', then<br> DrRacket it as an indication that the expression isn't finished, and so<br> it lets the user keep editing on the next line. Meanwhile, an<br> `exn:fail:read' exception other than the subtype `exn:fail:read:eof'<br> means that the read error should be reported to the user.<br> <div><div><br> <br> At Sun, 9 Dec 2012 19:03:44 -0500, Daniel Patterson wrote:<br> > I'm working (with sk and jpolitz) on a non-sexp language built on top<br> > of racket.<br> ><br> > We have basic support for it in the repl inside DrRacket, but none at<br> > all from the racket commandline repl (which also means no support for<br> > embedding inside other editors) - and the former seems to be using<br> > s-exps to figure out when to send the input to our eval (I think - I<br> > haven't found documentation describing how this works).<br> ><br> > So my question is:<br> ><br> > Is there a way to specify how input is split before sending to eval,<br> > both so that DrRacket could follow our conventions (which might, for<br> > example, match a "fun" with matching "end"), and so that the<br> > commandline repl knows how to split input at all (as right now it just<br> > keeps waiting for input until EOF - and EOF also causes the repl to<br> > quit!) Is there something that read/read-syntax should signal, or another<br> > handler to use?<br> ><br> > Thanks!<br> > Daniel<br> > ____________________<br> > Racket Users list:<br> > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a><br> ____________________<br> Racket Users list:<br> <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a><br> </div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br>Jay McCarthy <<a href="javascript:_e({}, 'cvml', 'jay@cs.byu.edu');" target="_blank">jay@cs.byu.edu</a>><br>Assistant Professor / Brigham Young University<br> <a href="http://faculty.cs.byu.edu/~jay" target="_blank">http://faculty.cs.byu.edu/~jay</a><br> <br>"The glory of God is Intelligence" - D&C 93<br> </div> </blockquote></div>