def test_trailing_bitcount():
assert trailing(0) == 0
assert trailing(1) == 0
assert trailing(-1) == 0
assert trailing(2) == 1
assert trailing(7) == 0
assert trailing(-7) == 0
for i in range(100):
assert trailing(1 << i) == i
assert trailing((1 << i) * 31337) == i
assert trailing(1 << 1000001) == 1000001
assert trailing((1 << 273956)*7**37) == 273956
# issue 12709
big = small_trailing[-1]*2
assert trailing(-big) == trailing(big)
assert bitcount(-big) == bitcount(big)
def trailing(n):
"""Count the number of trailing zero digits in the binary
representation of n, i.e. determine the largest power of 2
that divides n."""
n = int(n)
if not n:
return 0
low_byte = n & 0xff
if low_byte:
return small_trailing[low_byte]
# 2**m is quick for z up through 2**30
z = bitcount(n) - 1
if type(z) is int:
if n == 1 << z:
return z
t = 0
p = 8
while not n & 1:
while not n & ((1<<p)-1):
n >>= p
t += p
p *= 2
p //= 2
return t
def test_trailing_bitcount():
assert trailing(0) == 0
assert trailing(1) == 0
assert trailing(-1) == 0
assert trailing(2) == 1
assert trailing(7) == 0
assert trailing(-7) == 0
for i in range(100):
assert trailing((1 << i)) == i
assert trailing((1 << i) * 31337) == i
assert trailing((1 << 1000001)) == 1000001
assert trailing((1 << 273956)*7**37) == 273956
# issue 12709
big = small_trailing[-1]*2
assert trailing(-big) == trailing(big)
assert bitcount(-big) == bitcount(big)
def trailing(n):
"""Count the number of trailing zero digits in the binary
representation of n, i.e. determine the largest power of 2
that divides n.
Examples
========
>>> from sympy import trailing
>>> trailing(128)
7
>>> trailing(63)
0
"""
n = int(n)
if not n:
return 0
low_byte = n & 0xff
if low_byte:
return small_trailing[low_byte]
# 2**m is quick for z up through 2**30
z = bitcount(n) - 1
if type(z) is int:
if n == 1 << z:
return z
t = 0
p = 8
while not n & 1:
while not n & ((1<<p)-1):
n >>= p
t += p
p *= 2
p //= 2
return t
def trailing(n):
"""Count the number of trailing zero digits in the binary
representation of n, i.e. determine the largest power of 2
that divides n.
Examples
========
>>> from sympy import trailing
>>> trailing(128)
7
>>> trailing(63)
0
"""
n = int(n)
if not n:
return 0
low_byte = n & 0xff
if low_byte:
return small_trailing[low_byte]
# 2**m is quick for z up through 2**30
z = bitcount(n) - 1
if isinstance(z, SYMPY_INTS):
if n == 1 << z:
return z
t = 0
p = 8
while not n & 1:
while not n & ((1 << p) - 1):
n >>= p
t += p
p *= 2
p //= 2
return t
