Hi Ken.

Not to discourage people, but I have not seen cases where a "strong"

type system would be able to scale for _real_ Smalltalk applications.

You��re right. It doesn't. I'm not suggesting that.

The type safety is not for app-level Smalltalk development. It's for building the VM only.

I want to use the Pony concurrency model at the Smalltalk level. That��s the gist of it. Otherwise, I want a Smalltalk, not a statically compiled language.

Six ref-caps explicitly represent Pony��s concurrency model in code. They are essentially type qualifiers related specifically to concurrency. The plan is to reduce, if possible, the number of ref-caps the programmer must explicitly use/place in the code when coding a state-machine in Smalltalk, without producing a toy or straightjacket (without making it too simple or too rigid). This may require implementing the VM more as a change to (fork of) Pony instead of using Pony to implement the VM. I��m not sure yet.

The six ref-cap ideas for sharing data reliably between actors are not hard to grasp, but they take some getting used to, and involve some mental load. I don't want that much (concurrency-related or any other) implementation detail in the domain layer, much in the same vein as: I don��t use Forth because I don��t want to see stack acrobatics (ROTs and DUPs, etc.) amidst domain-level state-changes (FirePhotonTorpedo). It��s distracting. It dilutes focus on the domain work/layer, and tends to cause mistakes there.

The programmer��s domain logic and the concurrency-integrity provided by the ref-caps are different layers of thought and structure. The ref-caps are, however, mixed freely with domain logic in current Pony code. I think that��s a mistake. But that��s how it is now. I think of this layer mixing as an intermediate design stage of Pony. I want to abstract-out some or all ref-caps as the VM is built.

Pony language is not the remarkable thing here. I see it as a better C or better Rust. It��s very good (as Algol-60-ish-looking crap-syntaxes go), but that��s not what this is about. It��s about the actor programming, the concurrency model, and the guarantees given by use of the ref-caps. We would still obviously need to respect the Pony compiler��s determination of where ref-cap use is correct or not. Your Pony program won��t compile if you don��t use the ref-caps correctly, and you don��t get the guarantees or a running program without the compile. Much easier, therefore, might be to go the other way by changing Pony to support dynamic types without violating the invariants that allow the ref-caps (under the hood, abstracted out) to make the concurrency guarantees. Work Smalltalk dynamism into Pony, instead of building a Smalltalk VM with Pony.

Shaping

"Rational numbers"

(1/2) + (1/3) + (1/6). "--> 1 "

"Complex numbers"

[ :n | n * n] value: (-4 sqrt). "--> -4 "

"BigNums"

111 factorial. " -->

1762952551090244663872161047107075788761409536026565516041574063347346955087248316436555574598462315773196047662837978913145847497199871623320096254145331200000000000000000000000000

Just this is hugely complex to model in a "type safe" language.

Add metaprogramming (e.g. #doesNotUnderstand:), source level debugging of live stacks and GC of large object spaces and you have a very large

(space) and very slow (interlocking cache granularity) interpreter.

Please prove me wrong.

$0.02,

-KenD