[$] From late-bound arguments to deferred computation, part 2

Discussion on PEP 671 ("Syntaxfor late-bound function argument defaults") has been going on-in fits andstarts-since it was introduced lastOctober. The idea is to provide a way to specify the default for a function argument that is evaluated in thescope of the function call, which will allow more concise, and visible, defaults. But there hasbeen a persistent complaint that what thelanguage needs is a more-general deferred computation feature; late-bound defaults would simply fall out asone specific user of the feature. The arrival of a proposal for deferredcomputation did not really accomplish that goal, however.