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(define-library (csc strings)
(export
contains
find
join
not-found-error?
prefix?
split
str-quote)
(import (scheme base)
(only (scheme case-lambda) case-lambda)
(only (scheme write) write)
(only (csc list) intercalate)
(only (csc loop) loop))
(begin
(define prefix?
(case-lambda
((prefix str) (prefix? prefix str 0))
((prefix str start)
(and (<= (string-length prefix) (- (string-length str) start))
(string=? prefix (substring str start (+ start (string-length prefix))))))))
(define (str-quote s)
(let ((out (open-output-string)))
(write s out)
(get-output-string out)))
(define-record-type <not-found-error>
(make-not-found-error)
not-found-error?)
(define find
(case-lambda
((match str) (find match str 0 (string-length str)))
((match str start) (find match str start (string-length str)))
((match str start end)
(let loop ((i start))
(cond ((>= i end) (raise (make-not-found-error)))
((prefix? match str i) i)
(else (loop (+ 1 i))))))))
(define (contains s substr)
(if (string=? "" substr)
#t
(guard (e ((not-found-error? e) #f))
(find substr s)
#t)))
(define (join sep strings)
(apply string-append (intercalate sep strings)))
(define (split s sep)
(loop for s* = s then (string-copy s* (+ i (string-length sep)))
for i = (guard (e ((not-found-error? e) (string-length s*)))
(find sep s*))
collect (substring s* 0 i)
while (< i (string-length s*))))))
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