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;;; ps-string: string utilities for Pre-Scheme
(define (string-copy! target offset source start end)
(do ((tgt offset (+ tgt 1))
(src start (+ src 1)))
((= src end))
(string-set! target tgt (string-ref source src)))
(unspecific))
(define (string-append a b)
(let* ((len-a (string-length a))
(len-b (string-length b))
(target (make-string (+ len-a len-b))))
(string-copy! target 0 a 0 len-a)
(string-copy! target len-a b 0 len-b)
target))
(define (string-repeat source n)
(let* ((len (string-length source))
(total (* len n))
(target (make-string total)))
(do ((ix 0 (+ ix len)))
((= ix total))
(string-copy! target ix source 0 len))
target))
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