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(define-library (csc strings)
(export
contains?
has-prefix?
index
join
last-index
split
str-quote)
(import (scheme base)
(only (scheme case-lambda) case-lambda)
(only (scheme write) write)
(only (csc list) intercalate)
(only (csc loop)
loop
return))
(begin
(define (has-prefix? str prefix)
(and (<= (string-length prefix) (string-length str))
(string=? prefix (substring str 0 (string-length prefix)))))
(define (str-quote s)
(let ((out (open-output-string)))
(write s out)
(get-output-string out)))
(define (index s substr)
(loop for i from 0
for s = s then (string-copy s 1)
until (string=? "" s)
if (has-prefix? s substr)
return i
finally (return -1)))
(define (last-index s substr)
(loop for i downfrom (- (string-length s) (string-length substr)) to 0
if (has-prefix? (string-copy s i) substr)
return i
finally (return -1)))
(define (contains? s substr)
(if (string=? "" substr)
#t
(not (negative? (index s substr)))))
(define (join sep strings)
(apply string-append (intercalate sep strings)))
(define split
(case-lambda
((s sep n)
(if (= 0 n)
'()
(loop for n = n then (- n 1)
for s = s then (string-copy s (+ i (string-length sep)))
for i = (let ((i (index s sep)))
(if (or (negative? i)
(= 1 n))
(string-length s)
i))
collect (substring s 0 i)
while (< i (string-length s)))))
((s sep)
(split s sep -1))))))
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