Returns the complex arc tangent of its argument.

    This function is supported on OpenVMS Integrity servers and
    Alpha only.

    Format

      #include  <complex.h>

      double complex catan  (double complex z);

      float complex catanf  (float complex z);

      long double complex catanl  (long double complex z);

1 - Argument

 z

    A complex value.

2 - Description

    The catan functions compute the complex arc tangent of z, with
    branch cuts outside the interval [-i, +i] along the imaginary
    axis.

3 - Return Values

    n                  The complex arc tangent value, in the range
                       of a strip mathematically unbounded along the
                       imaginary axis and in the interval [-π/2,
                       +π/2] along the real axis.