How is your call stack represented? If you're representing
calls-in-scheme using calls-in-C, you might be in for an interesting
time. If you're representing calls-in-scheme as explicit activation
records on a stack maintained by the C code, you can capture that
structure alongside the environment, code pointer and other
virtual-machine registers to represent your continuation. (If it's a
real stack, you'll also need to deal with sharing issues; a simple thing
to do is to make the activation frames heap-allocated.)
If you're representing calls-in-scheme using calls-in-C, you might be
able to use a nifty setjmp/longjmp-plus-stack-copying trick I first saw
in Aubrey Jaffer's SCM interpreter back in the '90s:
http://cvs.savannah.gnu.org/viewvc/scm/scm/continue.c?revision=1.9&view=markup
(wow, still using CVS...)
Regards,
Tony
On 2011-03-08 10:58 PM, Patrick Li wrote:
Hello,
I'm programming a toy interpreter for Scheme for educational purposes.
It's programmed in C, and I've got a basic interpreter with the basic
forms working as well as tail call elimination.
I'm wondering, at this point, what's the easiest way to get call/cc
working? The interpreter is not programmed in CPS.
And can someone verify whether I'm understanding continuations properly?
Are they just essentially a "label"? That is, it's just some structure
that contains the next code to execute, and the environment in which to
execute that code in?
Thanks for your help
-Patrick
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