[e-lang] Causeway progress

[Terry Stanley]

The wiki page at <http://wiki.erights.org/wiki/Causeway> explains the
current state of Causeway.

The example used for the wiki discussion is a Joe-E/Waterken version
of our simple purchase order program. (Three queries are fired off
asynchronously and only if all return true -- the item's in stock, the
customer's credit is OK, the shipper can deliver -- is the order
placed.) It's a single vat example using promise-based eventual sends.


Thanks to Kevin Reid tracking down the SWT problem, Causeway now runs
on the Mac again.

Run this command to make a Mac application that can be launched from
the desktop.
    macify-swt.e
<e-source-directory>/e/src/esrc/scripts/causeway.e-swt
/Applications/causeway.app
When you quit Causeway, you may have to Force Quit SWT.


Highlights:

+ Causeway now supports both Ajax-style (one-way asynchronous
messages) and promises (where events have multiple causes).

+ Devora filter reduces noise by removing uninteresting nodes from the
graph before the views are constructed.

+ Stack Explorer shows the message chain and the relevant stack
traces. With the eventual sends and immediate calls the entire causal
chain can easily be followed.

More details to follow...

-- 
    Terry Stanley