On 4/16/07, skaller <[EMAIL PROTECTED]> wrote:
> In the model:
>
> spawn_fthread { Sin (xin, yout); };
>
> shows that a chip is different from a procedure.
> Here Sin is a *design* for a chip, but it is actually
> the fthread which is the chip: in other words,
> this is a dynamic instantiation of a template which not
> only creates an actual chip .. it also plugs it into
> the circuit by connecting particular wires to it.
This reminds me a lot of Pict [1]... Pict is based on the pi calculus
and has channels which are much like Felix's channels (except that
they are asynchronous). The equivalent of a "chip" is a "process
definition", with the difference being that processes are spawned once
each time they are needed, rather than running as a single-threaded
server. (In pi calculus this is represented as starting an infinite
number of single-threaded servers in parallel.)
> in Cauchy illustrates one of the problems. We're actually
> connecting here to a Newton chip which does this:
>
> var &b : double <- read bin;
> var &n : int <- read nin;
>
> It's vital that reads and writes be correctly ordered,
> or the circuit deadlocks.
This seems like Forth or assembler, where a failure to call a function
with the proper number of arguments in the proper order results in a
runtime error. I could be missing something, but why not just pass a
tuple? And for "variable-length" calls where you really want to read
items sequentially (as in the inner loop of Newton), you could pass a
channel to the process as an argument. That way you could take full
advantage of the type system to ensure that no deadlocks occur when
"calling" a process.
Overall I like the idea but I disagree that it's any more modular than
a good functional programming language. Functional module systems
such as O'Caml's really get to the heart of modularity: you can
manipulate both "ends" of a module functor the same way you can
manipulate the inputs and outputs of a chip. I'm at the tail end of a
course about component-based software engineering; I find it
fascinating how naturally the professor's "provides/requires" circuit
diagrams map to module functors... unfortunately the professor does
everything in Java so there's never any mention of such a relationship
:)
- Chris
[1] http://www.cis.upenn.edu/~bcpierce/papers/pict/Html/Pict.html
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