What if you have another program, written in C or something, that
monitors a file for changes, and if so changes the contents of
another file? Surely to catch that you must mark *all* file system
access as "interefering"? Even worse, another program could monitor
the state of a file and conditionally disable thet network driver,
now file access interferes with network access.
A compiler or runtime system can't know about these kinds of things --
unless perhaps you push the effect system into the operating system
(interesting idea). The best you can do is ensure the program itself
is correct in the absence of interference from other programs, but
there's no way to obtain a guarantee in the presence of interference.
Either with an effect system, or without (think of all the sequential
imperative code that gets broken when other programs concurrently
tamper with the file system or networking, etc.).
Regards,
John A. De Goes
N-Brain, Inc.
The Evolution of Collaboration
http://www.n-brain.net | 877-376-2724 x 101
On Aug 13, 2009, at 2:42 AM, Sebastian Sylvan wrote:
On Thu, Aug 13, 2009 at 4:56 AM, John A. De Goes <j...@n-brain.net>
wrote:
The next step is to distinguish between reading file A and reading
file B,
between reading file A and writing file A, between reading one part
of file A and writing another part of file A, etc. When the effect
system can carry that kind of information, and not just for files,
but network, memory, etc., then you'll be able to do some extremely
powerful parallelization & optimization.
What if you have another program, written in C or something, that
monitors a file for changes, and if so changes the contents of
another file? Surely to catch that you must mark *all* file system
access as "interefering"? Even worse, another program could monitor
the state of a file and conditionally disable thet network driver,
now file access interferes with network access.
--
Sebastian Sylvan
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