On 2018-05-11 22:12, Angus Hollands wrote:
while (value:=get_next_pool_item()) and value.in_use: print(value.refcount())
Just as a heads-up, I believe the prescribed way of doing that is: while (value := get_next_pool_item()).in_use: Of course you'd need additional mess to do something else with value. I don't like the asymmetry here: while (value := get_next_pool_item()).in_use and value is not blah:
Secondly, it reads in the order that matters. When reading the first line, one encounters what the condition is evaluating *first*, and then the implementation details (m=p.match) second. It reads as one would describe a mathematical equation in a paper, and clearly separates *what you're interested in* from *what it depends upon*. This is what I particularly dislike about the ":=" operator approach, the value, and name it is bound to, are unrelated at the point of evaluation, yet are right next to each other. It's visual noise. In the example above, the reader has to read the entire line when trying to find the loop condition.
I'm inclined to agree. But several people have argued that this is more readable than the alternative. I don't buy the reasoning, but they still like it better, and there's probably no point in going any further into this aspect. I doubt people are going to be convinced.
What am I getting at here? In effect, the "given" keyword provides a superset of use cases to that of ":=". Dare I say it, but *explicit is better than implicit*.
I'm not sure that it's strictly a superset. It's arguably the reverse, since it's restricted to statements with a condition rather than arbitrary expressions. I think the more important thing is that it's--subjectively--better at the subset of use cases that people seem to actually have (as listed in the OP).
*Readability:* A smaller point is that I don't feel that ":=" is very readable. If we had to use an operator, I think $= is better, but me reasoning for this is weak. I think it derives from my observation that ":=" is slow to distinguish from "=".
Clearly the objectively best choice is "<-".