This is a major change to the previous design, and also a change with
respect to the semantics in the ESOP 2016 paper. All the complexity of
echo-cancellation is stripped out of the core dataspace semantics, and
the relaying protocol is changed from one constructor, `at-meta`, to
two, `inbound` and `outbound`. The relay connecting a dataspace to its
container is now completely symmetric with the contained actors: it
initially asserts interest in what it is to relay, just like any other
actor would. Dataspaces no longer treat relaying specially.
This commit has updated all (I think) of the non-graphical examples. The
graphical code remains to be done in a following commit.
A store is like a parameter, except stores are independent of each
other, unlike parameters which are bundled together into a single
parameterization. This was observable in cases like the
example-action-after-suspension code checked in here, where dataflow
invoked a script, which parameterized current-dataflow-subject-id.
This captured *too much* of things like the pending-patch and
pending-actions. Subsequent `schedule-action!` calls' effects were
then lost.
Introduced expanders for events (define-event-expander) and for
assertion-patterns (define-assertion-expander).
Introduced convenience syntax and utilities in web.rkt for working
with web requests.
Support nested bindings in assertion-patterns for message events
(only).
Adding `#'module+` explicitly to the stop-list for local-expand stops
the infinite recursion (problem 1 in the issue description). The code
goes on to treat it like `#'module` and `#'module+`, namely as a
non-action-producing form.
Problem 2 in the issue description is interesting. I haven't done
anything in particular to address the production of unbounded `X` ->
`(begin X)` expansions, but it seems not currently to be a problem;
and, weirdly (?), submodules in a `#lang syndicate` or `#lang
syndicate/actor` module do not seem to inherit the `#%module-begin` of
their container! That is, `(module+ main)`, `(module+ test)` etc. all
seem to have a `racket/base` `#%module-begin`, though I've not looked
very far into this.
Most peculiar on this front is that if the `#,@(reverse final-forms)`
precedes the `(module+ syndicate-main ...)`, and the module being
processed includes, say, a `(module+ main)`, then for some reason the
resulting `main` submodule *is* treated as having a `syndicate/lang`
`#%module-begin` (thus causing problems as suggested in the issue
description)! I *really* don't understand why that might be, and
haven't spent very much time investigating after I noticed that so
long as the `main`-required `syndicate-main` submodule preceded all
other submodule declarations, things seemed to work out.
This whole approach is still a bit dicey: for example, the following
will erroneously treat `(foo quux)` as an expression yielding actions,
rather than a struct declaration:
#lang syndicate
(define-syntax-rule (foo x) (struct x ()))
(foo quux)