On Sat, 25 Dec 2010 15:18:07 -0700, Alex Khmara <[email protected]>
wrote:
On Sat, 25 Dec 2010 19:18:43 -0000, Robert Jacques <[email protected]>
wrote:
This @owned is very similar to previous 'scope' proposals (and oddly
dissimilar to previous owned proposals). To answer your question, under
previous proposals the scope keyword would allow you to declare that a
variable doesn't escape the current scope. So you could define external
functions that would take a 'scope int[]' and be guaranteed that it
wouldn't escape. (returning scoped values has to obey certain
restrictions)
The previous 'owned' proposals are a bit more general. Owned types
allow you parameterize a type on a variable, which sounds complex, but
what it means in terms of the runtime, is that all objects in the same
ownership group shared the same monitor. The big advantage is that
inside a synchronized method you don't have to synchronize other
'owned' objects of the same type. It also makes this like unique a lot
more viable, since you can now define trees, etc.
Ok, I'll try to find previous proposals about 'scope' - now I cannot
understand
how you can prevent external function from, e.g., saving owned object or
array (i.e. references)
in global variable, if it's at all possible to pass owned variables into
external functions.
Well, think about pure. A pure function can call other pure functions,
because those functions declare that they obey the rules of pure (i.e. no
globals, etc). Scope variables can be passed to functions taking scoped
parameters because those functions declare that they'll obey the rules of
scope (i.e. they won't squirrel away references to it, etc).
