integer type conversion problem/question

Paul invisiblepaul at hotmail.com
Sun Oct 10 12:38:14 CEST 2004


Faheem Mitha <faheem at email.unc.edu> wrote in message news:<slrncmgga6.dg0.faheem at Chrestomanci.home.earth>...
> On Sat, 09 Oct 2004 19:36:13 GMT, Faheem Mitha <faheem at email.unc.edu> wrote:
> > On Sat, 09 Oct 2004 19:31:30 GMT, Faheem Mitha <faheem at email.unc.edu> wrote:
> >
> >
> >> I did have one followup question. If Python implements its integers as
> >> signed C ints then surely 2^31 - 1 should be an integer rather than a
> >> long? But I get
> >>
> >>  In [9]: 2**31 - 1
> >>  Out[9]: 2147483647L
> >>
> >>  In [10]: type(2**31 - 1)
> >>  Out[10]: <type 'long'>
> >
> > Belated followup to my own message. The following behaves as expected.
> >
> > In [13]: 2147483647
> > Out[13]: 2147483647
> >
> > In [14]: 2147483648
> > Out[14]: 2147483648L
> >
> > Apparently there is something about the ** notation that makes Python
> > think of this as a long. Since Python people are more likely to know
> > the answer, I'm ccing comp.lang.python despite the followup. Thanks.
> 
> Eric Brewer kindly replied (directly to me), so I'm copying it here.
> 
> ********************************************************************
> This is because 2**31 is a long (and *then* you subtract 1)
> 
> >>> 2**31-1
>  2147483647L
> >>> 2**30
>  1073741824
> >>> 2**30 + 2**30
> 2147483648L
> 
> Here is one way to get 2**31-1 as a regular int:
> 
> >>> 2**30 + (2**30-1)
> 2147483647
> **********************************************************************
> 
> 

I'm sorry but this is off-topic in alt.comp.lang.learn.c-c++.
We do not discuss limbless reptiles in here. :)



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