I'm also using vat semantics inspired from E for my Reactive Demand Programming model, with great success.
I'm using a temporal vat model, which has a lot of nice properties. In my model:
- Each vat has a logical time (
getTime).- Vats may schedule events for future times (
atTime, atTPlus).- Multiple events can be scheduled within an instant (
eventually).- Vats are loosely synchronized. Each vat sets a 'maximum drift' from the lead vat.
- No vat advances past a shared clock time (typically, wall-clock). This allows for soft real-time programming.
This model is designed for scalable, soft real-time programming. The constraints on vat progress give me an implicit real-time scheduler (albeit, without hard guarantees), while allowing a little drift between threads (e.g. 10 milliseconds) can achieve me an acceptable level of parallelism on a multi-core machine.
Further, timing between vats can be deterministic if we introduce explicit delays based on the maximum drift (i.e. send a message of the form '
doSomething `atTime` T' where T is the sum of getTime and getMaxDrift.
assert( top( o-------o
|L \
| L \
| o-------o
| ! !
! ! !
o | !
L | !
L| !
o-------o ) == ( o-------o
| !
! !
o-------o ) );
In any language design, the total time spent discussing(source, via Debasish Ghosh)
a feature in this list is proportional to two raised to
the power of its position.
0. Semantics
1. Syntax
2. Lexical syntax
3. Lexical syntax of comments
(That is, twice as much time is spent discussing syntax
than semantics, twice as much time is spent discussing
lexical syntax than syntax, and twice as much time is
spent discussing syntax of comments than lexical syntax.)
