On Mon, 11 Oct 2021, Guido van Rossum wrote:
I always found the following more obvious:
def data_to_table(d: Iterable[Mapping[str, float]], *, sort: bool = False,
reversed: bool = False) -> Table:
...
@dataclass
class Stream:
converter: data_to_table | None
def add_converter(self, converter: data_to_table) -> None:
self.converter = converter
Another possibility would be that functions can't be used as their types
directly, but need a casting operator like so:
```
def add_converter(self, converter: typeof(data_to_table)) -> None:
self.converter = converter
```
It's too bad `type` is already taken, but `typeof` is what TypeScript calls
it: https://www.typescriptlang.org/docs/handbook/2/typeof-types.html --
perhaps there is a better distinguishing name, but I'll keep using `typeof`
for the sake of this discussion.
For static analysis, `typing.typeof` should only be used for variables that
are assigned (certain) constant values and aren't re-assigned.
Potentially this could be a much more general solution. Maybe interesting
return values for `typeof` could be defined for `dict`s, `namedtuple`s, etc.
And it could co-exist with the (P, Q) -> R proposal (which, as you probably
know, is how TypeScript expresses function types).
One disadvantage of this is that now arguments HAVE TO be named which
raises questions:
- should they be considered at type checking time?
- how to express "I don't care"?
I think it'd be natural for types constructed via `typeof` to include the
argument names; I'd intend for an object "just like" this one. But you could
imagine another type operator that drops details like this, e.g.
`typing.forget_argument_names(typing.typeof(data_table))`.
Erik
--
Erik Demaine | edema...@mit.edu | http://erikdemaine.org/
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