Re: [stack] Status of Cat and CVML

On Tue, Dec 30, 2008 at 2:39 PM, William Tanksley, Jr
<[email protected]> wrote:
> Christopher Diggins <[email protected]> wrote:
>> I am also working on adding portable continuations to Cat and CVML. I
>> expect to have the first prototype done by mid-February at the latest.
>> There are opcodes being introduced into the bytecode to allow
>> continuations (implemented by cloning the current VM state) to be
>> created, cloned, and serialized over a stream or network. In addition
>> I am adding an event passing mechanism to allow VM instances to
>> communicate safely and asynchronously.
>
> Nice! Parallelism will be important, and it looks like this might
> possibly help that.
>
> OTOH, I'm curious -- have you looked at partial continuations?
>
> http://en.wikipedia.org/wiki/Delimited_continuation

Yeah, I am not a huge fan of delimited continuations. They are quite
messy and unstructured.

> "Unlike regular continuations, delimited continuations return a value,
> and thus may be reused and composed."

Well this wikipedia entry is not entirely accurate. For example in C++
all programs return a value, so a continuation in a C++ program would
theoretically return a value (if we were allowed to have continuations
in C++ of course).

I do plan on allowing continuations to return values because all Cat
programs return a stack with a single value on the top. This means
that Cat continuations (in fact any Cat program) can be composed
together.

Another related feature I am working on for CVML is the ability to
chain programs together, and pipe the output from one into the input
of another as you can within Unix shells.

>> - Christopher
>
> -Wm