<HTML><BODY>In Common Lisp you have to use construction like (restart-case         (/ 1 x)      (use-value (value) "" value)) or cerror or something like that. I don't see, what prevents Racket to do the same: restart-case capture continuations and handler-case, handler-bind or debugger choose the continuation. Something like: (define (test l)   (if (null? l)       '()       (cons (let/cc k (with-handlers                           ([exn? (λ (v) (raise (cons v k)))])                         (/ 1 (car l))))             (test (cdr l))))) Then debugger can catch the continuation and call (k new-value). Четверг, 27 июня 2013, 13:32 -06:00 от Matthew Flatt <mflatt@cs.utah.edu>: <BLOCKQUOTE style="BORDER-LEFT: #0857a6 1px solid; PADDING-BOTTOM: 0px; MARGIN: 10px; PADDING-LEFT: 10px; PADDING-RIGHT: 0px; PADDING-TOP: 0px" class=mailru-blockquote> <DIV> <DIV class="js-helper js-readmsg-msg"> <STYLE type=text/css></STYLE> <DIV id=style_13723616850000000757 class=mr_read__body><BASE href="https://e.mail.ru/" target=_self> <DIV id=style_13723616850000000757_BODY>At Thu, 27 Jun 2013 12:35:10 -0400, Sean Kanaley wrote: > As a more general solution to this kind of interactive debugging issue, > how difficult would implementing a typical Common Lisp REPL be? I'm > thinking of adding the kind of error/condition handler like: > > "<error or condition goes here> > > enter a number: > > 0 - enter new value > 1 - exit to top level > 2 - exit one level > 3 - print stack trace > 4 - etc. > > I'm not familiar with Racket's internals so I don't know how much this > is a REPL hack vs. rewriting the whole system (the condition system > isn't necessary)... If it's not too impossible I would be happy to make > this contribution... Racket's implementation (and maybe to some degree, I think, its design) does not support restartable exceptions, except in the case of the `exn:break' exception. So, option 0 would be difficult or impossible to implement as a hook into the run-time system. A debugger could instrument programs to allow this kind of restart by wrapping every expression with a prompt, but I think that would be fairly expensive in the current implementation. ____________________   Racket Users list:   <A href="http://lists.racket-lang.org/users" target=_blank>http://lists.racket-lang.org/users</A> </DIV><BASE href="https://e.mail.ru/" target=_self></DIV></DIV></DIV></BLOCKQUOTE> -- Roman Klochkov </BODY></HTML>