tag—a go tag.
go transfers control to the point in the body
of an enclosing tagbody form labeled by a
tag eql to tag.
If there is no such tag in the body, the
bodies of lexically containing tagbody forms
(if any) are examined as well.
If several tags are eql
to tag, control is transferred to
whichever matching tag
is contained in the innermost tagbody form that
contains the go.
The consequences are undefined
if there is no matching tag lexically visible
to the point of the go.
The transfer of control initiated by go is performed
as described in Section 5.2 (Transfer of Control to an Exit Point).
(tagbody (setq val 2) (go lp) (incf val 3) lp (incf val 4)) → NIL val → 6
The following is in error because there is a normal exit
of the tagbody before the
go is executed.
(let ((a nil)) (tagbody t (setq a #'(lambda () (go t)))) (funcall a))
The following is in error because the tagbody is passed over
before the go form is executed.
(funcall (block nil
(tagbody a (return #'(lambda () (go a))))))