Tim Peters wrote:
> I don't think anyone has mentioned this yet, so I will: library
> writers using Decimal (or more generally HW 754 gimmicks) have a need
> to fiddle lots of thread-local state ("numeric context"), and must
> restore it no matter how the routine exits. Like "boost precision to
> twice the user's value over the next 12 computations, then restore",
> and "no matter what happens here, restore the incoming value of the
> overflow-happened flag". It's just another instance of temporarily
> taking over a shared resource, but I think it's worth mentioning that
> there are a lot of things "like that" in the world, and to which
> decorators don't really sanely apply.
To turn this example into PEP 340 based code:
# A template to be provided by the decimal module
# Context is thread-local, so there is no threading problem
def in_context(context):
old_context = getcontext()
try:
setcontext(context)
yield
finally:
setcontext(old_context)
Used as follows:
block decimal.in_context(Context(prec=12)):
# Perform higher precision operations here
Cheers,
Nick.
--
Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
---------------------------------------------------------------
http://boredomandlaziness.skystorm.net
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