On 2020-11-27 02:30, Ned Batchelder wrote:
On 11/26/20 9:02 PM, MRAB wrote:
On 2020-11-27 01:12, Ned Batchelder wrote:
On 11/26/20 6:44 AM, 3mi...@gmail.com wrote:
Add something like Move type hint to typing module. It will tell the
analyzer that the input parameter of the function is moved and can
not be used after. For example:
```
def f(d: Move[dict]) -> dict:
d['a'] = 2
return d
d = {1: 2}
f(d)
print(d[1]) # mistake, using of moved value
Maybe I'm behind the times on the latest thinking in programming
languages. I'm not familiar with "move semantics". Can someone explain
what is wrong with the code above? What is the mistake? `print(d[1])`
will work perfectly fine. The function changes the 'a' key, and then we
access the 1 key. Should the example have used the same key in both
places?
d is moved into function f. f does return d when it exits, moving it
out back again, but as the caller doesn't bind to it, it's discarded.
It's not discarded, it's still referenced by d in the outer scope.
No, it's not any more, and that's the point. It was _moved_ into the
function, and although the function returned it, it was discarded
because the caller didn't bind it to keep hold of it.
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