Although my posting to this list seems to tend to become
a somewhat autistic activity I'd like to reveal the 'mystery'
behind the script below:
http://esolangs.org/wiki/Fractran
http://en.wikipedia.org/wiki/FRACTRAN
Would writing a fractran interpreter in python be an interesting
project for teaching CS? (My first try below allows for a lot of
optimizations, e.g. not to use Fraction but resort to (long) ints.)
Best wishes,
Gregor
Gregor Lingl schrieb:
Hi all,
on vacation in the Tyrolean Alps one evening
I've found the time to implement another (I assume
less well known) idea of John Conway.
Just for fun.
from fractions import Fraction
fracs = [Fraction(f) for f in
"17/91 78/85 19/51 23/38 29/33 77/29 95/23 77/19 1/17 11/13 13/11
15/14 15/2 55/1".split()]
def fracgame():
z = Fraction(2,1)
while True:
for f in fracs:
n = z * f
if n.denominator == 1:
break
yield int(n)
z = n
def pow2(z):
n = 0
while z % 2 == 0:
n += 1
z //= 2
return (z == 1) * n
def what():
fg = fracgame()
while True:
z = next(fg)
n = pow2(z)
if n != 0:
yield n
what = what()
print(next(what))
print(next(what))
# the following will take 1 or 2 minutes
##w = 0 ##while w < 100:
## w = next(what)
## print(w)
Comments or discussion may follow when
I'm back to Vienna.
All the best,
Gregor
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