/usr/lib/s9fes/string-position.scm is in scheme9 2010.11.13-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 | ; Scheme 9 from Empty Space, Function Library
; By Nils M Holm, 2010
; See the LICENSE file of the S9fES package for terms of use
;
; (string-position string1 string2) ==> integer | #f
; (string-ci-position string1 string2) ==> integer | #f
; (string-word-position string1 string2) ==> integer | #f
; (string-ci-word-position string1 string2) ==> integer | #f
;
; (load-from-library "string-position.scm")
;
; Find the first occurrence of a small string STRING1 in a large
; string STRING2. Return the position of the first occurrence of
; STRING1 in STRING2 (positions start at 0). When STRING2 does not
; contain STRING1, return #F. STRING-CI-POSITION performs the same
; function, but ignores case.
;
; STRING-WORD-POSITION (STRING-CI-WORD-POSITION) differs from
; STRING-POSITION (STRING-CI-POSITION) in that is matches only full
; words, where a full word is a subsequence of characters that is
; delimited on both sides by one of the following:
;
; - the beginning of the string;
; - the end of the string;
; - a non-alphabetic character.
;
; Example: (string-position "ein" "gemeinsam") ==> 3
; (string-position "people" "democracy") ==> #f
; (string-word-position "me" "test me") ==> 5
; (string-word-position "me" "testme") ==> #f
(define (make-string-position p?)
(lambda (u s)
(let ((ks (string-length s))
(ku (string-length u)))
(let find ((i 0))
(cond ((> (+ i ku) ks)
#f)
((p? u (substring s i (+ i ku)))
i)
(else
(find (+ 1 i))))))))
(define (make-string-word-position p?)
(lambda (w s)
(let ((ks (string-length s))
(kw (string-length w)))
(let find ((i 0))
(cond ((> (+ i kw) ks) #f)
((and (p? w (substring s i (+ i kw)))
(or (zero? i)
(not (char-alphabetic?
(string-ref s (- i 1)))))
(or (= ks (+ i kw))
(not (char-alphabetic?
(string-ref s (+ i kw))))))
i)
(else
(find (+ 1 i))))))))
(define string-position (make-string-position string=?))
(define string-ci-position (make-string-position string-ci=?))
(define string-word-position (make-string-word-position string=?))
(define string-ci-word-position (make-string-word-position string-ci=?))
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