#localize correctness

[mentalisttraceur-software]

Python: just use `partial`!

One of my opinionated rules for making Python APIs intended for general use is to never take a callable and arguments to that callable in the same function signature, unless I need to modify those arguments before the callable gets them.

Every other alternative has some exception to what can be passed by position or by name, either to my function or through my function to the other callable. This is a trade-off which prioritizes common-case intuition and write convenience over the kind of logical regularity that helps ensure that code is actually correct in all cases.

Also, if I see

f(partial(g, foo, bar=qux))

then I know that `foo` and `bar=qux` are meant for `g` and not `f`, and that basically `f` has no say in the matter. But if I see

f(g, foo, bar=qux)

then I can't know from just the code logic if any of those arguments are intended for `g`, or if `f` will do something to them even if they are.

[mentalisttraceur-software]

Every time I read about Zig I get really positive feelings towards it until I hit something like "Zig avoids function colors", which just gives me the vibe of someone not understanding the whole point of function "colors" and why they are a good thing.

Forcing async-ness to be visible up the call tree lets you always know locally if something you are calling can modify state out from underneath you.

If every function call is potentially a point where another coroutine can get scheduled, as opposed to only the ones which say "await" in front of them, then that significantly increases all possibilities that need to be kept in mind.

It's still better than just preemptive concurrency where any state can change under you at literally any moment, but not by much.

Of course if you code cleanly and take the "share memory by communicating, don't communicate by sharing memory" then you shouldn't have that much shared state that could be changed out from under you, but in a language like Zig which targets the C niche, I would imagine that is still a bigger risk.