gcc/fortran/doc/gfortran/intrinsic-procedures/atan2d.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 .. _atan2d:
   7
   8 .. index:: ATAN2D
   9
  10 .. index:: DATAN2D
  11
  12 .. index:: trigonometric function, tangent, inverse, degrees
  13
  14 .. index:: tangent, inverse, degrees
  15
  16 ATAN2D --- Arctangent function, degrees
  17 ***************************************
  18
  19 .. function:: ATAN2D(Y, X)
  20
  21   ``ATAN2D(Y, X)`` computes the principal value of the argument
  22   function of the complex number X + i Y in degrees.  This function can
  23   be used to transform from Cartesian into polar coordinates and
  24   allows to determine the angle in the correct quadrant.
  25
  26   :param Y:
  27     The type shall be ``REAL``.
  28
  29   :param X:
  30     The type and kind type parameter shall be the same as :samp:`{Y}`.
  31     If :samp:`{Y}` is zero, then :samp:`{X}` must be nonzero.
  32
  33   :return:
  34     The return value has the same type and kind type parameter as :samp:`{Y}`. It
  35     is the principal value of the complex number X + i Y.  If :samp:`{X}`
  36     is nonzero, then it lies in the range -180 \le \atan (x) \leq 180.
  37     The sign is positive if :samp:`{Y}` is positive.  If :samp:`{Y}` is zero, then
  38     the return value is zero if :samp:`{X}` is strictly positive, 180 if
  39     :samp:`{X}` is negative and :samp:`{Y}` is positive zero (or the processor does
  40     not handle signed zeros), and -180 if :samp:`{X}` is negative and
  41     :samp:`{Y}` is negative zero.  Finally, if :samp:`{X}` is zero, then the
  42     magnitude of the result is 90.
  43
  44   Standard:
  45     GNU extension, enabled with :option:`-fdec-math`.
  46
  47   Class:
  48     Elemental function
  49
  50   Syntax:
  51     .. code-block:: fortran
  52
  53       RESULT = ATAN2D(Y, X)
  54
  55   Example:
  56     .. code-block:: fortran
  57
  58       program test_atan2d
  59         real(4) :: x = 1.e0_4, y = 0.5e0_4
  60         x = atan2d(y,x)
  61       end program test_atan2d
  62
  63   Specific names:
  64     .. list-table::
  65        :header-rows: 1
  66
  67        * - Name
  68          - Argument
  69          - Return type
  70          - Standard
  71
  72        * - ``ATAN2D(X, Y)``
  73          - ``REAL(4) X, Y``
  74          - ``REAL(4)``
  75          - GNU extension
  76        * - ``DATAN2D(X, Y)``
  77          - ``REAL(8) X, Y``
  78          - ``REAL(8)``
  79          - GNU extension
  80
  81   See also:
  82     Alias:
  83     :ref:`ATAND`
  84     Radians function:
  85     :ref:`ATAN2`