Use a frozenset for _stdlib_list_with_cache()

[AA-Turner]

cc @miketheman

Notionally it makes more sense to use a (frozen)set here, you can reconstruct the current representation via sorted(stdlib_set). However, stdlib_list() is a public function, so I've changed _stdlib_list_with_cache() to return a frozenset, and then used that in in_stdlib -- meaning we no longer need the LRU cache indirection.

A

[woodruffw]

Nice, makes sense to me! I think I'd be 100% okay with changing the stdlib_list return type too -- I suspect it'll be okay given that they're both sequences, and IMO we have some incompat breathing room since we're still pre 1.0.

(But I'll let @miketheman opine on that as well, I think this PR can go ahead regardless.)

[AA-Turner]

that they're both sequences

A frozenset isn't a sequence, you can't perform indexing operations on it. You could potentially create a new function for it, though (e.g. stdlib_names), which doesn't have 'list' in the name.

A

[AA-Turner]

Thanks for merging @woodruffw!

[woodruffw]

A frozenset isn't a sequence, you can't perform indexing operations on it. You could potentially create a new function for it, though (e.g. stdlib_names), which doesn't have 'list' in the name.

Ah yeah, I was thinking iterable. But you make a good point about it not being indexable; I hadn't thought through that and that would be a non-trivial public API change.