If VECTOR_A is integer or real then the result is the inner product of the two
arrays (i.e. the sum of the products of corresponding elements).
If VECTOR_A is complex then its conjugate is used in the inner product and the
result is the complex value that is the sum of the terms. If VECTOR_B =
VECTOR_A then the imaginary part of the result will be approximately zero.
If VECTOR_A is logical then the result is the same as ANY(VECTOR_A .AND.
If the vectors have size zero then the result is zero or false.