(+ number1 number2 [numbern ...])
This function returns the sum of all numbers given as arguments.
Examples
: (+ 5 2)
7
: (+ 1.2 3.4)
4.60
: (+ 5 1.2 2.8)
9.00
: (setq n1 (+ 1.2 5))
6.20
: (+ 3)
3