semantics of ** (unexpected/inconsistent?)

[Esmail]

Ok, this is somewhat unexpected:

Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.

-9

I would have expected the same result in both cases.

Initially I would have expected -3**2 to yield 9, but I can accept
that ** binds tighter than the unary -, but shouldn't the results
be consistent regardless if I use a literal or a variable?

 

[Alf P. Steinbach]

* Esmail:

Ok, this is somewhat unexpected:

Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.

-9

I would have expected the same result in both cases.

Initially I would have expected -3**2 to yield 9, but I can accept
that ** binds tighter than the unary -, but shouldn't the results
be consistent regardless if I use a literal or a variable?

It is.




I guess you expect your expression "x**2" to somehow be evaluated as "-3**2".
But x doesn't contain text, it contains an integer value that presumably (I
don't know) is represented in the binary number system, so it's evaluated as
"(-3)**2". If x contained text and was evaluated as such, pure text replacement,
then you should be able to write 2 x and have that evaluated as "2 -x"...


Cheers & hth.,

- Alf

 

[Mel]

Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.

-9

I would have expected the same result in both cases.

Initially I would have expected -3**2 to yield 9, but I can accept
that ** binds tighter than the unary -, but shouldn't the results
be consistent regardless if I use a literal or a variable?

When you say ** binds tighter than unary -, you're also saying that -3 isn't
a literal: it's an expression. Try

y=3
-y**2

Mel.