On Wed, Aug 3, 2011 at 7:24 PM, BGB <cr88...@gmail.com> wrote: > > If you have dynamic scope, you do not need TLS. > > > some people could potentially get annoyed or complain about having to > re-declare their thread-local dynamic variables when spawning a thread. >
The new thread should inherit the entire dynamic scope - logically, a local copy thereof. If there are object references mixed in, then the new thread now has a copy of these references, but the reference variables initially point to shared objects. Most of my earlier language designs (until late 2007) used a variation of dynamic scope <http://c2.com/cgi/wiki?ExplicitManagementOfImplicitContext> I developed in the context of distributed systems. I eventually eliminated it for two reasons: (1) Secure Interaction Design<http://people.ischool.berkeley.edu/~ping/sid/>. Dynamic scope violates the *path of least resistance, visibility, *and*awareness * properties. A lot of authority gets hidden inside the dynamic scope - hidden from both the sender and the potential user. (2) Many optimizations (memoization, caching, multi-cast and content-distribution, stable partial-evaluation and specialization), especially across module or distribution boundaries, are difficult unless we know exactly which parts of the input might influence the response. Today, I only allow explicit scope. Developers may explicitly model implicit context when they want it, similar to State monad in Haskell. Regards, Dave
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