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(define-library (csc strings)
(export
find
not-found-error?
prefix?
str-quote)
(import (scheme base)
(scheme case-lambda)
(only (scheme write) write))
(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))))))))))
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