c = zadd(a,b,[n])

Wrapper for ``zadd``.

Parameters
----------
a : input rank-1 array('D') with bounds (n)
b : input rank-1 array('D') with bounds (n)

Other Parameters
----------------
n : input int, optional
    Default: shape(a, 0)

Returns
-------
c : rank-1 array('D') with bounds (n)
