On Sat, Aug 8, 2020, 12:18 AM Ricky Teachey
> Yes, it's hard in the sense that it would require solving the halting
>> problem.
>>
>
> That doesn't sound so hard. ;)
>
> Thanks for educating me. Could it at least be useful for:
>
> 1. Providing semantic meaning to code (but this is probably not enough
> reason on its own)
> 2. Couldn't it still be useful for static analysis during runtime? Not in
> cpython, but when the type hints are used in cython, for example?
>
Being static like CPython doesn't help. You cannot know statically what the
result of an arbitrary computation will be.
There are certainly languages with guards. For example, Python. I can
definitely write a function like this:
def small_nums(i: int):
assert 0 < i < 100
do_stuff(i)
x = small_nums(arbitrary_computation())
In concept, an annotation could be another way to spell an assertion. But I
don't think we need that.
>
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