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(define-library (csc format)
(export
vfprintf
fprintf
vprintf
printf
vsprintf
sprintf)
(import (scheme base)
(only (scheme write) display)
(only (csc strings)
str-find
str-not-found-error?
str-prefix?))
(begin
(define (vfprintf port format-string format-args)
(let loop ((start 0)
(args format-args))
(cond ((>= start (string-length format-string)))
((str-prefix? "{{" format-string start)
(write-string "{" port)
(loop (+ 2 start) args))
((str-prefix? "}}" format-string start)
(write-string "}" port)
(loop (+ 2 start) args))
((str-prefix? "{}" format-string start)
(display (car args) port)
(loop (+ 2 start) (cdr args)))
((str-prefix? "{" format-string start)
(raise (error "invalid format string" format-string)))
(else
(let* ((open-brace-pos (guard (e
((str-not-found-error? e) (string-length format-string)))
(str-find "{" format-string start)))
(close-brace-pos (guard (e
((str-not-found-error? e) (string-length format-string)))
(str-find "}" format-string start)))
(format-pos (min open-brace-pos close-brace-pos)))
(write-string format-string port start format-pos)
(loop format-pos args))))))
(define-syntax fprintf
(syntax-rules ()
((_ port format-string format-args ...)
(vfprintf port format-string (list format-args ...)))))
(define (vprintf format-string format-args)
(vfprintf (current-output-port) format-string format-args))
(define-syntax printf
(syntax-rules ()
((_ format-string format-args ...)
(vprintf format-string (list format-args ...)))))
(define (vsprintf format-string format-args)
(let ((string-builder (open-output-string)))
(vfprintf string-builder format-string format-args)
(get-output-string string-builder)))
(define-syntax sprintf
(syntax-rules ()
((_ format-string format-args ...)
(vsprintf format-string (list format-args ...)))))))
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