Why do you need a weird two-phase reading system to deal with the EOF issue?
Robby On Monday, December 10, 2012, Jay McCarthy wrote: > 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 > <[email protected]<javascript:_e({}, 'cvml', '[email protected]');> > > 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 >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users >> > > > > -- > Jay McCarthy <[email protected] <javascript:_e({}, 'cvml', > '[email protected]');>> > Assistant Professor / Brigham Young University > http://faculty.cs.byu.edu/~jay > > "The glory of God is Intelligence" - D&C 93 >
____________________ Racket Users list: http://lists.racket-lang.org/users
