scsh-0.6/scheme/srfi/srfi-28.scm

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2002-09-11 10:34:58 -04:00
(define format
(lambda (format-string . objects)
(let ((buffer (open-output-string)))
(let loop ((format-list (string->list format-string))
(objects objects))
(cond ((null? format-list) (get-output-string buffer))
((char=? (car format-list) #\~)
(if (null? (cdr format-list))
(error 'format "Incomplete escape sequence")
(case (cadr format-list)
((#\a)
(if (null? objects)
(error 'format "No value for escape sequence")
(begin
(display (car objects) buffer)
(loop (cddr format-list) (cdr objects)))))
((#\s)
(if (null? objects)
(error 'format "No value for escape sequence")
(begin
(write (car objects) buffer)
(loop (cddr format-list) (cdr objects)))))
((#\%)
(newline buffer)
(loop (cddr format-list) objects))
((#\~)
(write-char #\~ buffer)
(loop (cddr format-list) objects))
(else
(error 'format "Unrecognized escape sequence")))))
(else (write-char (car format-list) buffer)
(loop (cdr format-list) objects)))))))