XPost: comp.lang.scheme

On 5/25/2024 3:34 PM, B. Pym wrote:

On 5/18/2024, HenHanna wrote:

-- Given a string 'a.bc.' -- replace each dot(.) with 0 or 1.

-- So the value is a list of 4 strings:
('a0bc0' 'a0bc1' 'a1bc0' 'a1bc1')

-- The order is not important.
If the string has 3 dots, the value is a list of length 8.

Gauche Scheme:

(use srfi-13) ;; string-count
(use util.combinations) ;; cartesian-product

(define (dot s)
(let ((b (cartesian-product (make-list (string-count s #\.) '(0 1))))
(fs (regexp-replace-all "[.]" s "~d")))
(map (cut apply format fs <>) b)))

(dot "a.b.c") ===> ("a0b0c" "a0b1c" "a1b0c" "a1b1c")

(dot "a.b") ===> ("a0b" "a1b")

(dot "ab.") ===> ("ab0" "ab1")

(dot ".ab") ===> ("0ab" "1ab")

(dot "ab") ===> ("ab")

Thank you!!! (map (cut ... is new to me. Did that come from MIT?



weird Gensym stuff!!!


(cut cons (+ a 1) <>) ≡ (lambda (x2) (cons (+ a 1) x2))

(cut list 1 <> 3 <> 5) ≡ (lambda (x2 x4) (list 1 x2 3 x4 5))

(cut list) ≡ (lambda () (list))




(cut <> a b) ≡ (lambda (f) (f a b))

;; Usage
(map (cut * 2 <>) ’(1 2 3 4))

(for-each (cut write <> port) exprs)

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