(defmacro compare-and-swap (place old new &environment env)
"Atomically stores NEW in PLACE if OLD matches the current value of PLACE.
Two values are considered to match if they are EQ. Returns the previous value
(defmacro compare-and-swap (place old new &environment env)
"Atomically stores NEW in PLACE if OLD matches the current value of PLACE.
Two values are considered to match if they are EQ. Returns the previous value