On Jul 1, 12:45 am, Mensanator <[EMAIL PROTECTED]> wrote:
> Here's an example.
> ...
> def partition_generator(depth,width):
> """creates all partions of a given depth,widtth (depth>=width)
> depth objects in width bins such that each bin has at least 1 object
> this function is a generator (does comb(depth-1,width-1) partitions)
>
> partition_generator(depth,width)
> depth: total inverse rule 1 count (p of 2**p)
> width: total inverse rule 2 count (q of 3**q)
> sv: sequence vector (the partition)
> returns sequence vector [sv]
> """
> def move_col(c):
> sv[c-1] += 1
> sv[c] -= 1
> def find_c():
> i = -1
> while i<0:
> if sv[i]>1:
> return i
> i -= 1
> def rollover(c):
> move_col(c)
> sv[-1] = sv[c]
> sv[c] = 1
> if depth<width: # error
> print 'depth',depth,'must be >= to width',width
> return # kills generator
> max_element = depth - width + 1
> sv = [1 for i in range(width)]
> sv[-1] = max_element
> yield sv[:] # first partition
> while sv[0]<max_element: # rest are generated by this loop
> c = find_c()
> if c < -1:
> rollover(c)
> yield sv[:] # must yield copy of sv, not sv
> else:
> move_col(c)
> yield sv[:]
It's just an example I know, but you can write this much more
cleanly...
def partitions(n, length):
"""Generate all sequences of positive numbers of the given
length that sum to n."""
assert 0 < length <= n
if length == 1:
yield [n]
return
for i in xrange(1, n + 2 - length):
for p in partitions(n - i, length - 1):
yield [i] + p
--
Paul Hankin
--
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