Terry Reedy wrote:
Ethan Furman wrote:
Anybody have an example of when the unary + actually does something?
Besides the below Decimal example. I'm curious under what circumstances
it would be useful for more than just completeness (although
completeness for it's own sake is important, IMO).
All true operators and some built-in functions translate to special
method calls.
-x == x.__neg__() == type(x).__neg__(x) == x.__class__.__neg__(x)
What should happen to '+x'? Raise SyntaxError? Ignore the '+'? Or
translate it to __pos__ in analogy with '-' and __neg__? Guido made the
third choice: partly for consistency perhaps, but also for the benefit
of user-written classes. Decimal started as user-contributed decimal.py.
Does anything else use this hook? I don't know, but I do know that
there are periodic demands for *more* operators for user use. So I
expect it has been.
tjr
It definitely makes sense from that perspective. As I was reading the
docs for numeric emulation I came across the unary + and wasn't sure
what to make of it. I tried it out, and got exactly what I put in, for
everything I tried. So I wondered if there were any situations where
you would get something besides what you started with.
Thanks to everyone for your comments and help.
--
Ethan
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