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
