Task handler abuse

basic-idea.lisp

(define-condition get-context (condition) 
  ())

(lparallel:task-handler-bind ((get-context (lambda (c) 
                                (declare (ignore c)) 
                                (invoke-restart 'receive :my-context))))
  (lparallel:pdotimes (i 5)
    (print (restart-case (signal 'get-context) (receive (value) value)))))

maybe-interface.lisp

;;; Shoud be used around sumitting tasks (include pdotimes and friends)
(defmacro with-context ((context) &body body)
  `(lparallel:task-handler-bind 
       ((get-context (lambda (c) 
                       (declare (ignore c))
                       (invoke-restart 'receive ,context))))
     ,@body))

;;; Can be called in tasks (in wokers)
(defun get-context () 
  (restart-case
      (signal 'get-context) 
    (receive (value)
	    value)))

usage.lisp

(with-context (:my-context) (lparallel:pdotimes (i 5) (print (get-context))))