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589 third
without running the epilogue code. If the loop terminates before expr is ever
evaluated, the epilogue code is run and the loop returns nil.
thereis expr is like (or exprl expr2 ... ). If the loop terminates before expr is ever
evaluated, thereis is like (or).
If you want a similar test, except that you want the epilogue code to run if expr
evaluates non-null, use until.
Examples:
(defun loop-thereis (my-list)
(loop for x in my-list
finally (print "what you going to do next 1")
do
(pri nc x) (pri nc " H)
do
and thereis (equal x 'a») => LOOP-THEREIS
(loop-thereis '(b c a e»
=> B CAT
(loop-thereis '(a a»
=> A T
See the section "loop Clauses", page 310.
third list Function
This function takes a list as an argument, and returns the third element of
the list. third is identical to
(nth 2 list)
The reason this name is provided is that it makes more sense when you
are thinking of the argument as a list rather than just as a cons.
For a table of related items: See the section "Functions for Extracting
From Lists" in Symbolics Common Lisp: Language Concepts.
throw tag value Special Form
Used with catch to make nonlocal exits. It flIst evaluates tag to obtain an
object that is the "tag" of the throw. It next evaluates form and saves the
(possibly multiple) values. It then finds the innermost catch (or zl:*catch)
whose "tag" is eq to the "tag" that results from evaluating tag. It causes
the catch (or zl:*catch) to abort the evaluation of its body forms and to
return all values that result from evaluating form. In the process, dynamic
variable bindings are undone back to the point of the catch, and any
unwind-protect cleanup forms are executed. An error is signalled if no
suitable catch is found.
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