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(define-module (Alpha String)
#:export (replace replace-char to-string str capitalize))
(define (replace-char s match repl)
(let ((f (lambda (a b)
(let ((next-char (if (eq? a match) repl a)))
(string-concatenate (list b (string next-char)))))))
(string-fold f "" s)))
(define (replace s match repl)
(string-replace-substring s match repl))
(define (to-string x)
(format #f "~a" x))
(define str
(case-lambda
(() "")
((x) (to-string x))
((x . rest) (string-concatenate (map str (cons x rest))))))
(define (capitalize s)
(let ((s (to-string s)))
(if (< (string-length s) 2)
(string-upcase s)
(str (string-upcase (substring s 0 1))
(substring s 1 )))))
;;; {String Fun: string-replace-substring}
;;;
;; string-replace-substring By A. Wingo in
;; https://lists.gnu.org/archive/html/guile-devel/2014-03/msg00058.html
;; also in string-replace-substring guix:guix/utils.scm.
(define (string-replace-substring str substring replacement)
"Return a new string where every instance of @var{substring} in string
@var{str} has been replaced by @var{replacement}. For example:
@lisp
(string-replace-substring \"a ring of strings\" \"ring\" \"rut\")
@result{} \"a rut of struts\"
@end lisp
"
(let ((sublen (string-length substring)))
(with-output-to-string
(lambda ()
(let lp ((start 0))
(cond
((string-contains str substring start)
=> (lambda (end)
(display (substring/shared str start end))
(display replacement)
(lp (+ end sublen))))
(else
(display (substring/shared str start)))))))))
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