Gigs_ wrote:
> Can someone explain me bitwise expression?
> few examples for every expression will be nice
>
> x << y Left shift
> x >> y Right shift
> x & y Bitwise AND
> x | y Bitwise OR
> x ^ y Bitwise XOR (exclusive OR)
> ~x Bitwise negation
>
>
> thanks people
Here's some examples:
## What is BINARY?
##
## n base 2
## -- --------
## 0 00000000
## 1 00000001
## 2 00000010
## 3 00000011
## 4 00000100
## 5 00000101
## 6 00000110
## 7 00000111
## 8 00001000
## 9 00001001
## 10 00001010
## 11 00001011
## 12 00001100
## 13 00001101
## 14 00001110
## 15 00001111
##
##
## What does << do?
##
## 00000111
## << 00000100
## ------------
## 01110000
##
## What does >> do?
##
## 00100100
## >> 00000010
## ------------
## 00001001
##
## What does & do?
##
## 00011011
## & 00001001
## ------------
## 00001001
##
## 00011011
## & 00001110
## ------------
## 00001010
##
## What does | do?
##
## 00010001
## | 00001010
## ------------
## 00011011
##
## 00011011
## | 00010001
## ------------
## 00011011
##
## What does ^ do?
##
## 00011011
## ^ 00011111
## ------------
## 00000100
##
## 00011111
## ^ 00001110
## ------------
## 00010001
##
## Bitwise demo: the Collatz Conjecture
##
## 41 31 47 71 107 161 121 91 137 103 155 233
## 175 263 395 593 445 167 251 377 283 425 319
## 479 719 1079 1619 2429 911 1367 2051 3077
## 577 433 325 61 23 35 53 5 1
bitwise.py
import gmpy # has lots of neat bitwise operations
# not found in standard Python
def convert_to_binary(n,bits):
s = gmpy.digits(n,2) # base 2 conversion
s = '0'*(bits-len(s)) + s # add leading 0's
return s
def report(n,m,o,p):
print ' %s' % (n)
print '%3s %s' % (o,m)
print '------------'
print ' %s' % (p)
print
def Collatz(n):
# if n is even, divide by 2
# if n is odd, multiply by 3 and add 1
# Collat Conjecture: n always reaches 1
while n>1:
# find bit position of LS 1 bit
f = gmpy.scan1(n)
if f == 0: # then n is odd
n = n*3 + 1
else: # n is even
# remove all factors of 2 in one fell swoop
n = n >> f
print n,
print
print 'What is BINARY?'
print """
n base 2
-- --------"""
for n in xrange(16):
print '%2d %s' % (n,convert_to_binary(n,8))
print
print
print 'What does << do?'
print
report(convert_to_binary(7,8), \
convert_to_binary(4,8), \
'<<', \
convert_to_binary(7<<4,8))
print 'What does >> do?'
print
report(convert_to_binary(36,8), \
convert_to_binary(2,8), \
'>>', \
convert_to_binary(36>>2,8))
print 'What does & do?'
print
report(convert_to_binary(27,8), \
convert_to_binary(9,8), \
'&', \
convert_to_binary(27&9,8))
report(convert_to_binary(27,8), \
convert_to_binary(14,8), \
'&', \
convert_to_binary(27&14,8))
print 'What does | do?'
print
report(convert_to_binary(17,8), \
convert_to_binary(10,8), \
'|', \
convert_to_binary(17|10,8))
report(convert_to_binary(27,8), \
convert_to_binary(17,8), \
'|', \
convert_to_binary(27|17,8))
print 'What does ^ do?'
print
report(convert_to_binary(27,8), \
convert_to_binary(31,8), \
'^', \
convert_to_binary(27^31,8))
report(convert_to_binary(31,8), \
convert_to_binary(14,8), \
'^', \
convert_to_binary(31^14,8))
print 'Bitwise demo: the Collatz Conjecture'
print
Collatz(27)
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