If you know that one item being compared is a symbol, use eq?:
(if (eq? operation '+) ...)
In general, for comparing simple items, use eqv?.
In the original definition of Lisp, data such as symbols, booleans,
and numbers were called atoms. In Common Lisp, an atom is defined
to be anything that is not a cons cell.
To compare list structure, strings, or vectors, use equal?.