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return-from name [result]
⇒ #<NoValue>
name—a block tag; not evaluated.
result—a form; evaluated. The default is nil.
Returns control and multiple values_2 from a lexically enclosing block.
A block form named name must lexically enclose the occurrence of return-from; any values yielded by the evaluation of result are immediately returned from the innermost such lexically enclosing block.
The transfer of control initiated by return-from is performed as described in Transfer of Control to an Exit Point.
(block alpha (return-from alpha) 1) ⇒ NIL
(block alpha (return-from alpha 1) 2) ⇒ 1
(block alpha (return-from alpha (values 1 2)) 3) ⇒ 1, 2
(let ((a 0))
(dotimes (i 10) (incf a) (when (oddp i) (return)))
a) ⇒ 2
(defun temp (x)
(if x (return-from temp 'dummy))
44) ⇒ TEMP
(temp nil) ⇒ 44
(temp t) ⇒ DUMMY
(block out
(flet ((exit (n) (return-from out n)))
(block out (exit 1)))
2) ⇒ 1
(block nil
(unwind-protect (return-from nil 1)
(return-from nil 2)))
⇒ 2
(dolist (flag '(nil t))
(block nil
(let ((x 5))
(declare (special x))
(unwind-protect (return-from nil)
(print x))))
(print 'here))
|> 5
|> HERE
|> 5
|> HERE
⇒ NIL
(dolist (flag '(nil t))
(block nil
(let ((x 5))
(declare (special x))
(unwind-protect
(if flag (return-from nil))
(print x))))
(print 'here))
|> 5
|> HERE
|> 5
|> HERE
⇒ NIL
The following has undefined consequences because the block form exits normally before the return-from form is attempted.
(funcall (block nil #'(lambda () (return-from nil)))) is an error.
block , return , Evaluation
Next: return, Previous: go, Up: Data and Control Flow Dictionary