iterating bit-by-bit across int?

[Jan Decaluwe]

Matthew Wilson wrote:
> I'm playing around with genetic algorithms and I want to write a
> function that mutates an integer by iterating across the bits, and about
> 1 in 10 times, it should switch a zero to a one, or a one to a zero.
> 
> I'm not sure how many bits are inside a python integer.  The library
> reference says at least 32.
> 
> I'm thinking about writing a function that eats integers and poops out
> lists of bools; and then I can iterate through that, and change values
> in there.  But before I do that, does anyone have a better idea?

You may be interested in the 'intbv' class that is part of my 'myhdl'
package for hardware design (link: see signature).

An intbv behaves like a Python long with an indefinite number of bits.
However, it is a mutable type that can also be used as a bitvector
through an indexing and slicing interface. Warning: slicing ranges are
downward as is common in hardware design but uncommon in Python.

Demo:

>>> from myhdl import intbv
>>> n = intbv(0xDE)
>>> n[:8] = 0xFA
>>> hex(n)
'0xFADEL'
>>> n[8:] = 0xB4
>>> hex(n)
'0xFAB4L'
>>> for bit in n[12:8]:
...     print bit
...
1
0
1
0
>>> n[123]
intbv(0L)
>>> n[123] = 1
>>> hex(n)
'0x800000000000000000000000000FAB4L'


Regards, Jan

-- 
Jan Decaluwe - Resources bvba - http://jandecaluwe.com
Losbergenlaan 16, B-3010 Leuven, Belgium
    Bored with EDA the way it is? Check this:
    http://jandecaluwe.com/Tools/MyHDL/Overview.html