Macro: SB-EXT:CAS

Synonym for COMPARE-AND-SWAP.

Additionally DEFUN, DEFGENERIC, DEFMETHOD, FLET, and LABELS can be also used to define CAS-functions analogously to SETF-functions:

(defvar foo nil)

(defun (cas foo) (old new) (cas (symbol-value ‘foo) old new))

First argument of a CAS function is the expected old value, and the second argument of is the new value. Note that the system provides no automatic atomicity for CAS functions, nor can it verify that they are atomic: it is up to the implementor of a CAS function to ensure its atomicity.

EXPERIMENTAL: Interface subject to change.

Lambda list

(sb-impl::place sb-impl::old sb-impl::new)