call-with-current-continuation

[Telford Tendys <telford@triangle.triode.net.au>]

>  > The one thing that most gets to me when writing scheme code is that
>  > C allows you to return from a function from anywhere you like and scheme
>  > requires that you structure it with (cond) and such. I find commands
>  > like `break', `continue' and `return' incredibly useful (is this just
>  > me?)
> 
> R4RS Scheme has call-with-current-continuation, which is much more flexible 
> than the jump instructions of imperative languages, at least is capable to
> emulate them.

It just so happens that I was reading R4RS just earlier today and thinking that
call-with-current-continuation looks pretty cool. Then I looked at the libguile
and found that call-with-current-continuation is not supported <sob>.

Actually, call-with-current-continuation is supposed to replace catch and
IMHO it is more useful than catch and it avoids the spewey dynamic-wind list
of tags and other such things that are entrenched in guile at this moment.

I also had a thought about errors... is it currently possible to override
the `error' procedure with your own error procedure and use this to redirect
all of the system errors? Is is safe to redefine `error' for some bits of
code and put back the global value for other sections?

If the error handling used call-with-current-continuation, could `error'
be made into a handy exit procedure that dropped back to whatever error
handling was activated at the time? Maybe this would offer application
developers an easy mechanism to customise guile error handling.

	- Tel