[ python-Feature Requests-1205239 ] Let shift operators take any integer value

[SourceForge.net]

Feature Requests item #1205239, was opened at 2005-05-19 19:54
Message generated for change (Comment added) made by dtorp
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=355470&aid=1205239&group_id=5470

Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Python Interpreter Core
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: David Albert Torpey (dtorp)
Assigned to: Nobody/Anonymous (nobody)
Summary: Let shift operators take any integer value

Initial Comment:
Let:  
    1 >> -4 
be interpreted as:
    1 << 4

This should be easy to do.  It would be somewhat helpful for 
bit manipulations and multiplying by powers of two.  Without 
the change, my code is laced with sections like:

if y > 0:
    z = x << y
else:
    z = x >> -y

This is ugly and slow compared to a straight:
   z = x << y

There is a precedent.  See what is done with negative list 
indices for comparison.  It saves even less code with  x[len
(x)-i] becoming x[i].  The reason for doing it is code 
simplication and clarity.


----------------------------------------------------------------------

>Comment By: David Albert Torpey (dtorp)
Date: 2005-05-27 17:05

Message:
Logged In: YES 
user_id=681258

Yes, I use this on long integers.  And, the whole point of doing 
shifts is to avoid the costs of computing and multiplying by 
powers of two.  Besides the math equivalents do not express the 
algorithms as well or as directly as shifts.

Other than coming up with cumbersome workarounds (which I 
already had), do you have an objection to letting the shift 
operators use negative indices (in much the same way as with 
array indices)?


----------------------------------------------------------------------

Comment By: Josiah Carlson (josiahcarlson)
Date: 2005-05-26 08:01

Message:
Logged In: YES 
user_id=341410

Is your code time critical?  Do your numbers have more than
53 bits of precision?  Do your numbers vary beyond 2**1024
or 1/2**1024?

If not, then the following should be sufficient for your
uses: int(x * 2**y)

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=355470&aid=1205239&group_id=5470