Greatest integer power of two less than or equal to positive n:
abjad> from abjad.tools import mathtools
abjad> for n in range(10, 20):
... print '\t%s\t%s' % (n, mathtools.greatest_power_of_two_less_equal(n))
...
10 8
11 8
12 8
13 8
14 8
15 8
16 16
17 16
18 16
19 16
Greatest-but-i integer power of 2 less than or equal to positive n:
abjad> for n in range(10, 20):
... print '\t%s\t%s' % (n, mathtools.greatest_power_of_two_less_equal(n, i = 1))
...
10 4
11 4
12 4
13 4
14 4
15 4
16 8
17 8
18 8
19 8
Raise type error on nonnumeric n.
Raise value error on nonpositive n.
Return positive integer.