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(define-library (csc list)
(export
revappend
split-at
take)
(import (scheme base))
(begin
(define (take n xs)
(let loop ((n n)
(xs xs)
(acc '()))
(if (or (not (positive? n)) (null? xs))
(reverse acc)
(loop (- n 1) (cdr xs) (cons (car xs) acc)))))
(define (split-at n xs)
(let loop ((n n)
(xs xs)
(acc '()))
(if (or (not (positive? n)) (null? xs))
(values (reverse acc) xs)
(loop (- n 1) (cdr xs) (cons (car xs) acc)))))
(define (revappend a b)
(let loop ((xs a)
(acc b))
(if (null? xs)
acc
(loop (cdr xs) (cons (car xs) acc)))))))
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