Messages (7) msg315688 - (view) Author: Kasra Vand (Kasra Vand) Date: 2018-04-24 07:31

Logical Negation of integers in Python always returns a Boolean result which can be achieve using `not`. Sometimes it's necessary to use this result directly in a proposition within a list comprehension (mostly). But if we use `not` directly in such arithmatic proposition it will raise a `SyntaxError.

```
In [46]: 3 + not(4)
  File "<ipython-input-46-e87dc6b7d800>", line 1
    3 + not(4)
          ^
SyntaxError: invalid syntax

```

Isn't that possible to make this work for integers in future releases? I was more curious to know what would be the drawbacks of such feature if there are any?

msg315689 - (view) Author: Kasra Vand (Kasra Vand) Date: 2018-04-24 07:35

This may seem not very useful while except 0 for other numbers it returns False but one may want to use another proposition inside `not` that can use either 0 or a nonzero number. Also, in this case we can form more comprehensive logical propositions.

msg315691 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * Date: 2018-04-24 07:59

You can use 3 + (not 4).

msg315694 - (view) Author: Kasra Vand (Kasra Vand) Date: 2018-04-24 11:21

Thanks, Indeed. But my question is more about the syntax and why it's not that straight? The reasons for that is because Python is known as a scientific programming language and many people come with mathematical background and may want to use this kind of syntax.

So is it possible to add this feature?

msg315696 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * Date: 2018-04-24 11:51

If `3 + not 4` be accepted, should it be evaluated to the same value as `not 4 + 3`? Currently the result of `not 4 + 3` is False.

msg315697 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * Date: 2018-04-24 11:54

And consider the example `3 + not 4 + 5`.

msg315699 - (view) Author: Kasra Vand (Kasra Vand) Date: 2018-04-24 12:48

I think this will contradict to Python's operators precedence. What I mentioned seems like you're passing the number as an argument to `not`, and this is while `not` is not a function. There is an `operator.not_` function that does the same job as expected though.

Now I see why it's not efficient and wise to do so. This is violation of  operators precedence.