vector a:
Array
(
    [0] => 2
    [1] => 3
    [2] => foo
    [3] => 5.5
    [4] => 43.3
    [5] => 21.11
)
----
vector b -> a notice (b = log(Π) * a)
Erbegnis vector b:
Array
(
    [0] => 2.2894597716988
    [1] => 3.4341896575482
    [2] => 0
    [3] => 6.2960143721717
    [4] => 49.566804057279
    [5] => 24.165247890281
)
----
vector c - a warning
NULL
----
vector d - fatal error
array(6) {
  [0]=>
  float(NAN)
  [1]=>
  float(NAN)
  [2]=>
  float(NAN)
  [3]=>
  float(NAN)
  [4]=>
  float(NAN)
  [5]=>
  float(NAN)
}
/