Re: legitimate closure?

Mirko.Vukovic@xxxxxxxxx writes:

This closure works on clisp on cygwin+windows:
cl-user> (let ((list (list 1 2 3 4 5))
(item 4))
(delete item list :test #'(lambda (unused b) (= item b))))
(1 2 3 5)

I used closure for lambda to get "item" from delete's first argument

Why? DELETE already pass it to your TEST function, in the UNUSED
parameter, since you gave ITEM to DELETE.


The straightforward version is
cl-user> (let ((list (list 1 2 3 4 5))
(item 4))
(delete item list :test #'(lambda (a b) (= a b))))

I'm not sure why would this ever be useful, but I was surprised that
lambda captured it.

It did not. You passed explicitely ITEM to DELETE, and DELETE passes
it explicitely to your TEST function.


C/USER[6]> (let* ((list (list (cons 1 1) (cons 2 2) (cons 3 3) (cons 4 4) (cons 5 5)))
(item (fourth list)))
(delete item list :test (lambda (a b)
(print `(is a identical to item? --> ,(eq a item)))
(print (member b list))
(eq a b))))

(IS A IDENTICAL TO ITEM? --> T)
((1 . 1) (2 . 2) (3 . 3) (4 . 4) (5 . 5))
(IS A IDENTICAL TO ITEM? --> T)
((2 . 2) (3 . 3) (4 . 4) (5 . 5))
(IS A IDENTICAL TO ITEM? --> T)
((3 . 3) (4 . 4) (5 . 5))
(IS A IDENTICAL TO ITEM? --> T)
((4 . 4) (5 . 5))
(IS A IDENTICAL TO ITEM? --> T)
((5 . 5))
((1 . 1) (2 . 2) (3 . 3) (5 . 5))



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