On 2008 Sep 1, at 18:08, Ganesh Sittampalam wrote:
On Mon, 1 Sep 2008, John Meacham wrote:
On Mon, Sep 01, 2008 at 10:45:05PM +0100, Ganesh Sittampalam wrote:
Actually all this use of the tainted and derogatory term "global
variable" is causing me to be imprecise. All MVars/IORefs have
"global"
main/process scope whether or not they're bound to something at the
top level.
"Global variable" is exactly the right term to use, if we are
following
the terminology of other languages. We don't call the result of
malloc/new etc a "global variable", unless it is assigned to
something
with top-level scope.
global variable is not a very precise term in other languages for
various platforms too a lot of times. for instance, windows dll's
have
the ability to share individual variables across all loadings of said
dll. (for better or worse.)
Interesting, is this just within a single process?
Last I checked, it was across processes; that is, every DLL has its
own (optional) data segment which is private to the DLL but shared
across all system-wide loaded instances of the DLL. This actually
goes back to pre-NT Windows.
Haskell certainly has more advanced scoping capabilities than other
languages so we need a more refined terminology. I think 'IO scope'
is the more precise term, as it implys the scope is that of the IO
monad state. which may or may not correspond to some external
'process scope'.
Hmm, to me that implies that if the IO monad stops and restarts,
e.g. when a Haskell library is being called from an external
library, then the scope stops and starts again (which I presume is
not the intention of <- ?)
It tells me the flow of execution has temporarily exited the scope of
the IO monad, but can return to it. The state is suspended, not exited.
--
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] [EMAIL PROTECTED]
system administrator [openafs,heimdal,too many hats] [EMAIL PROTECTED]
electrical and computer engineering, carnegie mellon university KF8NH
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