XPost: comp.lang.scheme

Pascal Costanza wrote:

(let* ((temp1 (mapcar #'f1 some-list))
(temp2 (mapcar #'f2 temp1))
(temp3 (mapcar #'f3 temp2)))
(mapcar #'f4 temp3))

You could better say:

(loop for elem in some-list
collect (f4 (f3 (f2 (f1 elem)))))

(map (~> abs sqrt list) '(-4 -9 25))

===>
((2) (3) (5))

Given:

(define-syntax ->>
(syntax-rules ()
[(_ x) x]
[(_ x (y ...) z ...)
(->> (y ... x) z ...)]
[(_ x y z ...)
(->> (y x) z ...)]))

(define-syntax ->
(syntax-rules ()
[(_ x) x]
[(_ x (y more ...) z ...)
(-> (y x more ...) z ...)]
[(_ x y z ...)
(-> (y x) z ...)]))

;; currying
(define-syntax ~>
(syntax-rules ()
[(_ func0 func ...)
(lambda xs (-> (apply func0 xs) func ...))]))

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XPost: comp.lang.scheme

B. Pym wrote:

(loop for elem in some-list
collect (f4 (f3 (f2 (f1 elem)))))

(map (~> abs sqrt list) '(-4 -9 25))

===>
((2) (3) (5))

(map (~> abs sqrt list (append '(finished))) '(-4 -9 25))
===>
((2 finished) (3 finished) (5 finished))

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