CL-STM

Interface 

Composing 

(defmacro try (&body body)
  "Return a transaction that executes each transaction in BODY
atomically from left to right until one succeeds.

The return value of the transaction is the value of the
transaction that succeeds."
  (reduce [list 'orelse] body :from-end t))

Retrying 

(defun retry ()
  "Return a transaction that when executed, aborts the current
transaction and re-executes it from scratch.

The transaction will wait on all variables that have been read so
far during the transaction."
  (trans (throw 'retry (current-tlog))))

Lifting 

(defmacro trans (body)
  "Create a new anonymous transaction."
  `(new 'standard-transaction
        :thunk
        (lambda ()
          ,body)))

(defun untrans (transaction)
  (funcall (thunk-of transaction)))

Defining 

(defmacro deftransaction (name (&rest args) &body body)
  "Define a new transaction called NAME.

DEFTRANSACTION is just like DEFMETHOD but the body is walked into
an STM action."
  `(progn
     (eval-always
       (pushnew ',name *trans-funs*))
     (defmethod ,name ,args
       ,(stm `(progn ,@body)))
     ',name))