gcc/fortran/doc/gfortran/intrinsic-procedures/popcnt.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
   5
   6 .. index:: POPCNT, binary representation, bits set
   7
   8 .. _popcnt:
   9
  10 POPCNT --- Number of bits set
  11 *****************************
  12
  13 .. function:: POPCNT(I)
  14
  15   ``POPCNT(I)`` returns the number of bits set ('1' bits) in the binary
  16   representation of ``I``.
  17
  18   :param I:
  19     Shall be of type ``INTEGER``.
  20
  21   :return:
  22     The return value is of type ``INTEGER`` and of the default integer
  23     kind.
  24
  25   Standard:
  26     Fortran 2008 and later
  27
  28   Class:
  29     Elemental function
  30
  31   Syntax:
  32     .. code-block:: fortran
  33
  34       RESULT = POPCNT(I)
  35
  36   Example:
  37     .. code-block:: fortran
  38
  39       program test_population
  40         print *, popcnt(127),       poppar(127)
  41         print *, popcnt(huge(0_4)), poppar(huge(0_4))
  42         print *, popcnt(huge(0_8)), poppar(huge(0_8))
  43       end program test_population
  44
  45   See also:
  46     :ref:`POPPAR`,
  47     :ref:`LEADZ`,
  48     :ref:`TRAILZ`