

def  _snake_case		(snake_case_					:     float  )							->		int:
  if num < 0:
    return -1
  return 1 if num else 0





def  _snake_case		()							->		None:
  assert signum(5  ) == 1
  assert signum(-5  ) == -1
  assert signum(0  ) == 0


if __name__ == "__main__":
      print(signum(1_2))
      print(signum(-1_2))
      print(signum(0))








from __future__ import annotations





def  _snake_case		(snake_case_					:     str  )							->		bool:
  __UpperCAmelCase	:  int
  __UpperCAmelCase	:  list[str]		=     list(snake_case_  )
  __UpperCAmelCase,			__UpperCAmelCase	:  Any		=     _vector[:-1], int(_vector[-1]  )
  __UpperCAmelCase	:  list[int]		=     [int(snake_case_  ) for digit in __vector]

  vector.reverse()
  for i, digit in enumerate(snake_case_  ):
    if i & 1 == 0:
      __UpperCAmelCase	:  int		=     digit * 2
      if doubled > 9:
        doubled -= 9
      check_digit += doubled
    else:
      check_digit += digit

  return check_digit % 10 == 0


if __name__ == "__main__":
      import doctest

      doctest.testmod()
      assert is_luhn('''79927398713''')
      assert not is_luhn('''79927398714''')





