On Tue, Jun 21, 2022 at 5:53 PM Brendan Barnwell brenbarn@brenbarn.net wrote:
In the example, we assume that the built-in function `type()` is special in not counting as a reference to the binding for purpose of realizing a computation. Alternately, some new special function like `isdeferred()`
might be used to
check for ``Deferred`` objects.
I'll have to ponder my thoughts about the proposal as a whole, but this particular aspect seems dubious to me. As I understand it this would require some fairly deep changes to how evaluation works in Python. Right now in an expression like `type(blah)`, there isn't any way for the evaluation of `blah` to depend on the fact that it happens to occur as an argument to `type`.
I absolutely agree that this is a sore point in my first draft. I could shift the magic from `type()` to `isdeferred()`, but that doesn't really change anything for your examples. I suppose, that is, unless `isdeferred()` becomes something other than a real function, but more like some sort of macro. That doesn't make me happy either.
However, I *would* like to be able to answer the question "Is this object a DeferredObject?" somehow. For example, I'd like some way to write code similar to:
if isdeferred(expensive_result): log.debug("The computationally expensive result is not worth calculating here") else: log.debug(f"We already hit a path that needed the result, and it is {expensive_result}")
Any thoughts on what might be the least ugly way to get that?