bitwise shift?

[desktop]

I have found a code example with this loop.

for k in range(10, 25):
n = 1 << k;


I have never read Python before but is it correct that 1 get multiplied
with the numbers 10,11,12,12,... ,25 assuming that 1 << k means "1 shift
left by k" which is the same as multiplying with k.

[Michael Hoffman]

Re: bitwise shift?

desktop wrote:

I have found a code example with this loop.
>
for k in range(10, 25):
n = 1 << k;
>
>
I have never read Python before but is it correct that 1 get multiplied
with the numbers 10,11,12,12,... ,25

No.

assuming that 1 << k means "1 shift left by k"

Yes.

which is the same as multiplying with k.

No.

Try starting the Python interpreter and entering 1 << 10.
--
Michael Hoffman

[=?ISO-8859-1?Q?Thomas_Kr=FCger?=]

Re: bitwise shift?

desktop schrieb:

I have found a code example with this loop.
>
for k in range(10, 25):
n = 1 << k;
>
>
I have never read Python before but is it correct that 1 get multiplied
with the numbers 10,11,12,12,... ,25 assuming that 1 << k means "1 shift
left by k" which is the same as multiplying with k.

1 << n
is a more efficient replacement for
2**n

Thomas

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[Sherm Pendley]

Re: bitwise shift?

desktop <fff@sss.comwri tes:

for k in range(10, 25):
n = 1 << k;
>
I have never read Python before but is it correct that 1 get
multiplied with the numbers 10,11,12,12,... ,25 assuming that 1 << k
means "1 shift left by k" which is the same as multiplying with k.

Shift left is *not* the same as multiplying by k. It is the same as multi-
plying by 2^k. That is, 1<<10 = 1024, 1<<11 = 2048, 1<<12 = 4096, etc.

sherm--

--
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Cocoa programming in Perl: http://camelbones.sourceforge.net

[Terry Reedy]

Re: bitwise shift?


"desktop" <fff@sss.comwro te in message
news:f0of5a$nn9 $1@news.net.uni-c.dk...
|I have found a code example with this loop.
|
| for k in range(10, 25):
| n = 1 << k;
|
|
| I have never read Python before but is it correct ...

One of the super-nice feature of Python is the interactive mode, also
available with IDLE and other IDEs. that lets you explore the meaning of
Python code faster than you can ask here. Use it and learn.

>>for k in range(10, 25): print 1 << k

1024
2048
4096
8192
16384
32768
65536
131072
262144
524288
1048576
2097152
4194304
8388608
16777216

[John Machin]

Re: bitwise shift?

On 26/04/2007 7:10 AM, Sherm Pendley wrote:

Shift left is *not* the same as multiplying by k. It is the same as multi-
plying by 2^k.

Where I come from, ^ is the exclusive-or operator. Of course YMMV in WV :-)

[Sherm Pendley]

Re: bitwise shift?

John Machin <sjmachin@lexic on.netwrites:

On 26/04/2007 7:10 AM, Sherm Pendley wrote:
>

>Shift left is *not* the same as multiplying by k. It is the same as multi-
>plying by 2^k.

>
Where I come from, ^ is the exclusive-or operator. Of course YMMV in WV :-)

Make that YMMV in VB. :-(

Funny thing is, I haven't written in VB since '95 or thereabouts. Let that be
a lesson for the youngsters - touch not the unclean beast called VB, lest its
vileness stain thy code for all time!

sherm--

--
Web Hosting by West Virginians, for West Virginians: http://wv-www.net
Cocoa programming in Perl: http://camelbones.sourceforge.net

[Tobiah]

Re: bitwise shift?

John Machin wrote:

On 26/04/2007 7:10 AM, Sherm Pendley wrote:
>

>Shift left is *not* the same as multiplying by k. It is the same as
>multi-
>plying by 2^k.

>
Where I come from, ^ is the exclusive-or operator. Of course YMMV in WV :-)

desktops:toby:g abc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
2^3
8

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[Tobiah]

Re: bitwise shift?

Tobiah wrote:

John Machin wrote:

>On 26/04/2007 7:10 AM, Sherm Pendley wrote:
>>

>>Shift left is *not* the same as multiplying by k. It is the same as
>>multi-
>>plying by 2^k.

>>
>Where I come from, ^ is the exclusive-or operator. Of course YMMV in
>WV :-)

>
desktops:toby:g abc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
2^3
8
>

Wow, thunderbird displayed this to me as a true exponent, even
though it is an ascii message. anyone else get this?


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[mensanator@aol.com]

Re: bitwise shift?

On May 2, 2:24 pm, Tobiah <t...@tobiah.or gwrote:

John Machin wrote:

On 26/04/2007 7:10 AM, Sherm Pendley wrote:

>

Shift left is *not* the same as multiplying by k. It is the same as
multi-
plying by 2^k.

>

Where I come from, ^ is the exclusive-or operator. Of course YMMV in WV :-)

>
desktops:toby:g abc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
2^3
8

OTOH,

IDLE 1.2c1

>>2^3

1

Guess which one is relevant to comp.lang.pytho n?

>
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[Adonis Vargas]

Re: bitwise shift?

Tobiah wrote:
<snip>

Wow, thunderbird displayed this to me as a true exponent, even
though it is an ascii message. anyone else get this?
>
>

Yeah I can confirm Thunderbird 1.5.10 on Linux.

Adonis