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Re: feature?
Lynn Winebarger <owinebar@free-expression.org> writes:
> Would anyone else be interested in having guile return a continuation
> if it recieves an interrupt signal? I've been doing some stuff with it
> that makes my system go swap-crazy, and I'd like to be able to stop it in
> the middle of the computation, look at what it's doing, and then restart
> it from there.
Three weeks ago I asked about such a feature. So I would be
interested. On the other hand, it may be non-trivial. Here, the
answer by Telford Tendys:
# I doubt that it is possible, a longjmp() call is used for errors and
# it isn't usually reversable. The documentation for setjmp() and
# longjmp() doesn't make it clear what happens when you try pinging
# back and forth between two of them but my guess is that it fails.
# However the call/cc system is better because it makes a full copy of the
# stack so you can be sure that everything will be available next time
# you want it. I suggest that you find a logical division in your calculation
# and then use call/cc to get a continuation which you can jam into a global
# variable. Don't do this too often or the garbage collector will eat all your
# time but do it often enough that you can restart without too much lost
# calculation.
# Another alternative is to replace the normal error handler with one that
# piles MORE on the stack rather than the standard one which drops back.
# Some LISP systems and some other schemes do this, I'm sure it wouldn't be
# hard to write one like this for guile. What basically happens is that a
# new REPL is started on top of the existing calculations so that you are
# still at the same place inside the calculations. On a good day you can
# debug back down the stack that you are sitting on, change a few variables
# and set it going again.
# - Tel
Nicolas.