On Aug 14, 2009, at 9:07 PM, Sebastian Sylvan wrote:
That's a separate issue. The problem is that if you *do* depend on outside "interference", then the sequence of operations matters.
You're example is highly contrived. Were I designing an effect system, I would not design for programs that require outside interference through a medium as uncontrolled as the file system, because (1) if there are applications requiring such measures, they are few and far between, and (2) you cannot make any guarantees about the correctness of programs depending on interference through an uncontrolled medium. Effect system optimizations are about taking programs that are correct, and transforming them to faster but equivalent programs that are still correct. That said, your reasoning precludes the use of file read buffering, and other similar operations that are routinely done. It's only an illusion that such programs are "safe", with or without transformation of sequential read operations. Regards, John A. De Goes N-Brain, Inc. The Evolution of Collaboration http://www.n-brain.net | 877-376-2724 x 101