description:
addition(seq, seq)
the addition function
takes element-wise sum of the coefficients
examples:
addition(3|a> + 1.2|b>, 3.5|a> + 0.9|b> + 5.13|c>)
6.5|a> + 2.1|b> + 5.13|c>
see also:
intersection, union, complement, multiply