mensanator at aol
Aug 22, 2008, 4:10 PM
Post #4 of 4
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On Aug 22, 5:43 pm, "Medardo Rodriguez (Merchise Group)"
<med....@gmail.com> wrote:
> On Fri, Aug 22, 2008 at 6:30 PM, defn noob <circularf...@yahoo.se> wrote:
> > What does >> and << do?
>
> Normally they are bitwise operators:>> Shifts bits right
>
> << Shifts bits left
>
> print 1 << 3
> 8
>
> because 8 = 00001000 in binary
>
> Regards
An example of usage:
import gmpy
def Collatz(n):
#
# if n is odd, multiply by 3 and add 1
# if n is even, divide by 2 until n becomes odd
# repeat until n == 1
#
while n>1:
print n,
f = gmpy.scan1(n) # find position of first 1-bit
if f>0: # it's even, so...
n = n >> f # ...remove factors of 2 in one fell swoop
else: # it's odd
n = 3*n + 1
print n
print 'Collatz(11):',
Collatz(11)
print
print 'Collatz(27):',
Collatz(27)
## Collatz(11): 11 34 17 52 13 40 5 16 1
##
## Collatz(27): 27 82 41 124 31 94 47 142 71
## 214 107 322 161 484 121 364
## 91 274 137 412 103 310 155
## 466 233 700 175 526 263 790
## 395 1186 593 1780 445 1336
## 167 502 251 754 377 1132 283
## 850 425 1276 319 958 479 1438
## 719 2158 1079 3238 1619 4858
## 2429 7288 911 2734 1367 4102
## 2051 6154 3077 9232 577 1732
## 433 1300 325 976 61 184 23 70
## 35 106 53 160 5 16 1
--
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